Could _ have been _ who helped Sunny get her work done?A.they ,it B.they ,them C.it,them D.it,they 答案是 D为啥?

If it _ for the rain,we _ the picnic yesterday.A were not; could have hadB were not; could haveC had not been; could have had Have you ever been to a concert?(作否定回答)No,_ _ / _ ,_. Have you ever been to a concert?(作否定回答)No,_ _ / _ ,_. 英语填写句子1.I don't care _ _ _ _ _ 是不是下雨2.I wonder _ _ _ _ 是真的还是假的or not3.did you ask the teacher _ _ _ _ 我们什么时候进行英语测验to have an English exam4.could you tell me _ _ _ _ _ _我们从这到公园 Could _ have been _ who helped Sunny get her work done?A.they ,it B.they ,them C.it,them D.it,they 答案是 D为啥? I have been collecting shells for three tear and a half同义句转换I have been collecting shells for _ _ _ _. could I borrow your(_ _ _ _r_)? -Could you help me ,please?-_ _ _ _a_ _ _ Complete the sentences withhave/has been to/in,have gone to,go.How long _ you _ this village? where _ he he_to the library.A have been,went B have been ,have been C has been,went继续上面的“D has been,has been >_ >_ (×_×) :>_ (@_@) -_-|| (>_ >_