1Theinstrumentswillhavetobecarefullytestedbeforethey.AarebeingusedBwillbeusedCcanbeusedDuse2"DidyoutelephonetheGovernor'soffice?""Yes,hebackbeforetomorrownoon."AexpectsBisexpectedCexpectedDist

Question

1 The instruments will have to be carefully tested before they________.
A are being used B will be used C can be used D use
2 "Did you telephone the Governor's office?"
"Yes,he_________back before tomorrow noon."
A expects B is expected C expected D is to expect
请解释一下该答案正确的原因和错误答案错误的原因,
What_________(do)______________.(can not ,undo)

Answer 1

1.C 这些设备（或器材）在可以投入使用之前必须经过仔细的测试.
A表示正在进行时,没有必要.B没有可以投入使用的意思.D就不用说了吧~
2.B 预计他（是我们预计他,所以是被动的）在明天下午之前就能回来is expected back=is expected to be back.首先这里应该是被动的,所以AC排除.D表示将来要...没有将会期望的说法,而且也是主动的,
3. can't be undone什么事情是不能不做的?这里主语是‘事情’,而事情是被做的,所以是被动语态.