4. It was wrong to drop litter on the street, ________?

The correct answer is c. wasn't it. *Explanation:* This is a tag question. The main clause is positive ("It was wrong to drop litter on the street"), so the tag question should be negative. The auxiliary verb used is "was", and the subject is "it". Therefore, the correct tag is "wasn't it?". *Translation:* Было неправильно мусорить на улице, не так ли?