When is your parents' birthday 对么?

问题描述:

When is your parents' birthday 对么?

不对,因为父母不应该只有一个生日,应该写“When are your parents' birthday?"

既然是”parents“就应该是复数,两个日子,所以应该是
”when are your parents‘ birthday“

When is your parent's birthday ?
When are your parents' birthdays ?
当然,如果父亲和母亲的生日是同一天的话,就用楼主的这个句子