__either your parents or your elder brother to blame for your being late?

答案应该是are，这个题目考的是临近原则，谓语动词和最靠近谓语的名词保持一致，因此用are是由your parents决定的。这个句子如果变成肯定句的话，就要变成：Either your parents or your elder brother [is] to blame for your being late.

Are
相信我没错～ 哈哈
真的，因为your parentS = >1人

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1

are,根据就近原则

is 还原后就近原则

1.这是把句子Either my parents or my elder brother is to blame for my being late.变为一般疑问句，所以应选1．