Fact 1: Microorganisms can cause infections. Fact 2: Moisture is required for the microorganisms to grow. Given the two facts above, _ can cause infections to grow.?

Choices:
1). Pesticides.
2). bacteria.
3). influenza.
4). nitric oxide.
5). disease.
6). carbon dioxide.
7). moisture.
8). oxygen.
The answer is:
7).