Câu 19: Not only _____________ in the project, but he also wanted to become the leader. A. did Jack involve B. had Jack been involved C. was Jack involved D. have Jack involved Câu 20: _________________ , sheep were then used for wool. A. Having first domesticated for milk production B. Because they had been first domesticated for milk production C. Having been first domesticated for milk production D. Although they had first domesticated for milk production