I ___ out when the phone rang

happen
happened
happened to
happened to he

happened to he
这里的be 和后面out 构成“在外面”的意思
happen to do 是“恰好在做某事”的意思
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第1个回答  2010-03-17
happened to be
第2个回答  2010-03-17
happened to he
第3个回答  2010-03-17
happened

记住when的两边通常是对应的,
因为ring用过去时rang,所以happen也用过去时happened