Definition: You are given a question on virology. You are also given 4 answer options (associated with "A", "B", "C", "D"), out of which only one is correct. You need to answer the question by selecting the correct option. You should only answer with the choice letter, not the whole answer.
Input: Are/were viruses:
(A)The most abundant form of life on earth? (B)Discovered before bacteria? (C)Grown in animals in the laboratory? (D)The cause of all human disease?

A