How long have your son had yellow hair?错在哪里
问题描述：
How long have your son had yellow hair?错在哪里
答
一楼对的，2楼那个没学过现在完成式的别乱说
答
How long has your son had yellow hair? (不要告诉我这句是英语考试里的题,太傻了.虽然这样说没错了,但听起来怪怪的.还是下面这样说自然一点）
For how long since your son has had yellow hair?
答
How long has your son had yellow hair?
这个句子考的是how long后面的人称表示，既然主语是your son，所以have应该变为has。
这个句子回答成：My son has had yellow hair for one year.
这样一来，你就明白为什么用has了。
答
how long has your son had yellow hair?
答
How long since your son had yellow hair.
have 和had 不能同时用
答
how long has your son had yellow hair?
have 变 has