The correct response is period. This would be the smallest measurement of time given the answer choices. 

The order from longest to shortest is shown here: Supereon > Eon > Era > Period

The correct response is era because it represents longer periods of time on the geological time scale. The answer choicest from longest to shortest are as follows: Era > Period > Epoch > Age.

The law of superposition states that the oldest rock layers are at the bottom. A real world example of this often takes place while cooking. When making a seven-layer dip, for instance, you place the oldest layer on the bottom of the dish and stack layers on top. The layer on top is the youngest. The earth is made of rock layers deposited in a similar way.

E represents a period of erosion, meaning there is "missing time" (rock layers have been eroded, so there are no rocks representing that time). 

The three main rock types are sedimentary, igneous, and metamorphic. Sedimentary rock is the result of the build up of sediment, such as sand or dirt. Igneous rocks are the result of the cooling of lava and molten rock, and can be crystalline in structure. Metamorphic rock is the compression of igneous and/or sedimentary rock, creating a new type of rock from intense pressure. Metamorphic rock comprises the majority of the Earth's crust.

As rocks travel further from the original outcrop, bumps and abrasions round corners and polish the rock. 

Increasing temperature and pressure—through burial or submersion—causes the minerals that compose the rock to become unstable. This results in recrystallization of the minerals, which forms a new rock.

The question indicated that the rock melted completely. When a partially melted rock recrystallizes, it becomes a metamorphic rock; however, when a rock completely melts and any crystallization occurs, it results in the production of an igneous rock.

Weathering is a process that creates sediment. There are physical and chemical weathering processes. On the other hand, erosion is described as a process that transports sediment. Erosion transports sediment through exogenous processes, such as by water or wind.

The freeze-thaw cycle acts like a chisel that produces fractures throughout the rock. Water rests in cracks on the rock’s surface and when it freezes it expands and causes more fractures. Water can then lay in these new fractures and further weather or crack the rock. This example represents a physical weathering process.

Rocks can transition between sedimentary, metamorphic, and igneous rocks. Sedimentary rock forms from the weathering of any rock type. Igneous rock forms from the melting of any rock type. Metamorphic forms from recrystallization (without melting) any type of rock.