If you have promised to come,you will not ．A.back upB.back awayC.back downD.back
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If you have promised to come,you will not ________．
A.back up
B.back away
C.back down
D.back out
试题答案
D
back out是“决定不履行(诺言)”的意思，题目的意思是“如果你答应了来，就不要食言”。