Viruses are not considered to be living things, but they depend upon living cells for energy, reproduction, and protection at the expense of the cells that they invade.

the type of relationship described could best be classified as one of.

a)
commensalism.

b)
mutualism.

c)
parasitism.

d)
resignation.

The answer should be C. Parasitism

Yeah the answer is C
This of it this way 
Parasitism: One is only happy not both =) =(

mutualism: Both are happy =) =)

commensalism: one is happy the other is fine =) =|

resignation: Is say if a snake was trying to eat a monkey but the monkey was moving too fast the snake would eventually give up and find something else to eat.
Hope this helps =)