Q: You are presented with the quiz "What can some viruses cause?"   But you don't know the answer, so you turn to your teacher to ask for hints. He says that "some viruses can cause cancer" and "cancer requires an accumulation of mutations".   So, what's the best answer to the question?

Pick from:
 (1). explosions
 (2). anemia
 (3). extinction
 (4). Dehydration
 (5). birth
 (6). bacteria
 (7). mutations
 (8). Allergies
The answer is:
(7).