A . haveB . areC . hav

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A . have
B . are
C . have been
D . has been

参考答案:

参考答案:D

参考解析:
遇到not only...but also的句型时,谓语动词的单复数与靠近它的名词一致。Old wiring是单数,谓语动词为单数。选项D是正确的。句子大意:不光是开关,就连旧的线也换了。