You are a scientist trying to develop a technology that can be used to power wrist watches. which type of electromagnetic wave would be most useful to investigate?

EMF radiations

Explanation:

Electric and magnetic fields (EMFs) radiation is a terms collectively used for invisible energy waves governed by electricity and magnetic forces. These radiations are usually produced when some thing is operated by use of electrical power.

In watches , mercury or other ionizing battery cells are used to power the watch and hence it can be stated that EMF radiation are most useful to investigate.

Some time high frequency waves such as ultraviolet rays and X-rays are considered as form of EMF waves

parasites can detrimentally affect their host, but also must not allow their host to die before they can complete their life cycle. some parasites have complex life cycles with many different hosts, and have had to find ways of persisting in many different environments during the change from one host to another. ectoparasites live outside the body of the host, and can more easily  disperse, but are  more exposed to predators, parasites, parasitoids. endoparasites live inside the body of the host, and are therefore protected from the outside environment. but they can be  attacked by the host's immune system. they have therefore developed  mechanisms for dispersal such as  complex life cycles.

your answer should be c) enjoy!