This question tests understanding of nuclear decay and radioactivity, specifically the concept of half-life and activity calculations. After one half-life (59 days), Seed 1 will have half its original activity. After two half-lives (118 days), Seed 2 will have undergone two halvings: (1/2) × (1/2) = 1/4 of its original activity. Since both seeds started with identical initial activity, Seed 2 will have half the activity of Seed 1 at their respective times of use. Choice A is correct because Seed 2 has experienced one additional half-life compared to Seed 1. Choice D is incorrect because it compares Seed 2's activity to the original activity rather than to Seed 1's activity at 59 days.

This question tests understanding of nuclear decay and radioactivity, specifically electron capture. In electron capture, a proton in the nucleus captures an inner orbital electron and converts to a neutron, emitting a neutrino. When Cr-51 undergoes electron capture to V-51, the atomic number decreases by 1 (from 24 for chromium to 23 for vanadium) while the mass number remains at 51. Choice A is correct as it accurately describes the conversion of a proton to a neutron and the resulting decrease in atomic number. Choice B is incorrect because it describes beta-minus decay (neutron to proton conversion), which is the opposite process.

This question tests understanding of sequential nuclear decay processes. In ⁶⁰Co decay, β- emission occurs first, converting ⁶⁰Co to ⁶⁰Ni* (excited state) by changing a neutron to proton, thus changing the element. The excited ⁶⁰Ni* then undergoes gamma decay to ground state ⁶⁰Ni, releasing energy without changing nuclear composition. Choice A correctly describes beta emission changing the element followed by gamma emission relaxing the daughter nucleus. Choice B reverses the sequence impossibly, choice C gives incorrect mass changes, and choice D incorrectly relates emission order to particle speed. When analyzing decay chains, beta decay changes element identity while subsequent gamma decay only changes energy state.

This question tests understanding of beta-minus decay and conservation laws. In β- decay of ¹³¹I to ¹³¹Xe, a neutron converts to a proton: n → p + e- + ν̄e. This increases atomic number from 53 (iodine) to 54 (xenon) while mass number remains 131, conserving baryon number. An electron is emitted to conserve charge. Choice A correctly describes mass number conservation at 131, atomic number increase by 1, and electron emission. Choice B incorrectly suggests neutron emission, choice C describes alpha decay, and choice D is physically impossible. When verifying nuclear reactions, check that mass number, charge, and baryon number are conserved on both sides of the equation.

This question tests understanding of alpha decay and its nuclear changes. Alpha particles are helium-4 nuclei (²He⁴) containing 2 protons and 2 neutrons. When emitted, the parent nucleus loses these 4 nucleons, decreasing atomic number by 2 and mass number by 4. This explains alpha particles' high mass and charge, leading to high linear energy transfer and short tissue range. Choice A correctly describes the loss of 2 protons and 2 neutrons with corresponding decreases in atomic and mass numbers. Choice B incorrectly suggests gaining nucleons, choice C describes a different process, and choice D incorrectly places alpha emission outside the nucleus. When analyzing alpha decay, remember the emitted particle is a complete helium nucleus.

This question tests understanding of radioactive decay over multiple half-lives. With t₁/₂ = 110 min and transport time = 220 min, exactly 2 half-lives have elapsed (220/110 = 2). After one half-life, 50% remains; after two half-lives, 25% remains. The formula is: fraction remaining = (1/2)^(t/t₁/₂) = (1/2)² = 1/4 = 25%. Choice A correctly identifies that 25% remains after two half-lives. Choice B incorrectly ignores time dependence, choice C miscalculates the fraction, and choice D incorrectly counts three half-lives. When calculating remaining activity, always determine the number of half-lives as t/t₁/₂ and apply $(1/2)^n$.

This question tests understanding of gamma decay characteristics. Gamma decay involves emission of a high-energy photon from an excited nucleus transitioning to a lower energy state. Unlike particle emission, gamma decay doesn't change the number of protons or neutrons, so both atomic number and mass number remain constant. The nucleus retains its identity but loses energy. Choice A correctly describes photon emission with unchanged nuclear composition. Choice B describes β- decay, choice C describes alpha decay, and choice D describes β+ decay. When analyzing gamma decay, remember it's purely an energy transition without changing nuclear constituents.

This question tests understanding of half-life calculation from decay constant. The relationship is t₁/₂ = ln(2)/λ, where ln(2) ≈ 0.693. With λ = 0.0866 h⁻¹, t₁/₂ = 0.693/0.0866 ≈ 8.0 h. This follows directly from the exponential decay law where half the nuclei decay when e^(-λt₁/₂) = 1/2. Choice A correctly calculates half-life as approximately 8 h using t₁/₂ = ln(2)/λ. Choice B incorrectly inverts the formula, choice C gives an arbitrary result, and choice D incorrectly claims initial activity is needed. When calculating half-life from decay constant, always use t₁/₂ = ln(2)/λ ≈ 0.693/λ.

This question tests understanding of beta-minus decay and nucleon conservation. In β- decay, a neutron converts to a proton (n → p + e- + ν̄e), increasing atomic number by 1 while mass number remains constant since the total number of nucleons (protons + neutrons) is unchanged. The emitted electron is not a nucleon and doesn't affect mass number. Choice A correctly describes mass number conservation with atomic number increase due to neutron-to-proton conversion. Choice B incorrectly suggests mass number decrease, choice C reverses the process, and choice D incorrectly identifies beta particles as photons. When analyzing β- decay, remember that nucleon number (mass number) is conserved while proton number (atomic number) increases by 1.

This question tests understanding of beta-minus decay at the nucleon level. The transformation n → p + e- + ν̄e shows a neutron converting to a proton, which increases the atomic number by 1 (gaining a proton) while mass number remains unchanged (total nucleons constant). The emitted electron carries away negative charge to conserve charge. Choice A correctly describes atomic number increase by 1 with unchanged mass number. Choice B reverses the process, choice C describes alpha decay, and choice D incorrectly assigns charge to the neutrino. When analyzing β- decay, remember it always involves neutron-to-proton conversion, increasing atomic number by 1.