1. C. come - are going to miss

• The first blank requires a present tense verb, as the bus is coming right now. "Come" is the correct choice.
• The second blank needs a future tense to express a future action that is likely to happen. "Are going to miss" is the appropriate choice.

So, the sentence becomes: "Here, come our bus. Hurry up! We are going to miss it."

1. A. has been polluted

• This sentence requires a perfect tense to express an action that started in the past and continues to the present. "Has been polluted" is the correct choice, indicating that the river has been polluted for a significant period of time.

So, the sentence becomes: "The river has been polluted by poisonous chemicals for a long time."