3. The polluted water kills many fish, ________?

The correct answer is d. doesn't it. *Explanation:* This is a tag question. The main clause is positive ("The polluted water kills many fish"), so the tag question should be negative. The subject is "the polluted water", which is singular, so we use "does". The correct tag is "doesn't it?". *Translation:* Загрязненная вода убивает много рыбы, не так ли?