题目内容
This building is both a secret and a mystery. No one shall be admitted into it ______ he can give the right password.
| A.if | B.as | C.since | D.unless |
D
考查连词。句意为这幢楼是一个秘密和迷。没有人可以被允许进入,除非他可以得到正确的密码。
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