A musician performs a concert, so the answer must be something that a dancer performs. While you might think that “gyration” would work, this is a specific action, not a type of event (like concert). Thus, “ballet” is the best answer for this. Even though all dancers do not necessarily perform ballets, this option alone establishes a parallel with dancer in a manner similar to the relationship between musician and concert.

"Cardiovascular" is a medical term relating to the "heart," just as "pulmonary" refers to the "lungs."

The cardiologist is a specialist at studying the heart. The word itself as a root for “heart” in it—namely, “card-.” A “cardiac arrest” occurs when the heart suddenly stops beating. An “ecologist” is one who studies the environment, generally speaking. An ecosystem, for example, is the whole system of organisms and material environment in a given area. While each of the other options are part of the environment and animals therein, none of them is equivalent to the environment in general.