Which best shows a harmful effect of a mutation?

The correct answer will be option in which mutation is observed in the legs of the frog.

Explanation:

The mutation is a change which takes place in the sequence of DNA. When it takes place in the segment of DNA which can code the trait, it is expressed in the trait.  

These mutation can prove beneficial to the organisms but can also become lethal to the organisms like the one with a mutation in legs of the frog as the legs of the frog helps provide the ability to move as well to swim in the water. if the legs will show a trait of mutation, the frog will not be able to swim and move properly.  

Thus, option in which mutation is observed in the legs of the frog is the correct answer.

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.

it would be c. xylem.