In this section, you will hear one passage. At the end of the passage, you will hear four questions. Both the passage and the questions will be spoken only once. After you hear a question, you must choose the best answer from the four choices marked A), B), C) and D).A、Algae may help the growth of bacteria.
B、It can be contaminated by chlorine.
C、Animals may drink it.
D、It can be contaminated by rain.