Question

13.They..........a lot of books.were soldsellshave sellhave sold​

Answer 1

They have sold a lot of books.

Факт, без индикатора времени = present perfect

Answer 2

Ответ:

13.They have sold a lot of books.

Answer 3

The correct answer is: have sold

The sentence should be: "They have sold a lot of books." This is in the present perfect tense, indicating an action that started in the past and has relevance to the present moment.