问题
Why didn’t you go to Shelly’s birthdayparty yesterday evening—I ______ but I had an unexpected visitor
A:when
B:while
C:unless
D:which
B:while
C:unless
D:which
正确答案是：
同类题型
Charles Darwin considered ______ to be theprocess by which evolution took place.
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This dress is too expensive. Do you have others— Sorry, but that’s the __________ one.