21- Active: Scientists find solutions to problems.
passive: Solutions to problems are found by scientists.
22- D. 23-B. 24-B. 25-C. 26-B. 27-C.
28- would ask.
29- was damaged.
30- Doesn't he ?
31- will she ?
32- When were these expensive houses bought?
33- my brother went to the library,but he didn't study.
34-b. 35-d. 36-C. 37-b.
با آرزوی بهترین ها برای شما🌹🙂
