9.Every boy and girl must have ____?hair neatly combed.

9.Every boy and girl must have ____?hair neatly combed.
A.his
B.her
C.its
D.their?
为什么选A而不是D?求详解,

9. Every boy and girl must have ?____? hair neatly combed.?
A. his B. her C. its D. their?
为什么选A而不是D?求详解,谢谢
答：楼主能问这个问题,说明是有一定了解的.
本题设计有误.AD都可能,最佳答案我认为应为D.
Every boy and girl 相当于Everyone 作主语.后面的人称代词以前可以用his, 后来因为女权主义运动,改用his or her 或用their
《Longman》词典上everybody同条目下有一个usage:
Anybody, every, and everybody are followed by a singular verb. They are sometimes followed by a plural pronoun A. (非正式) to avoid saying he or she, since there is no one word for this in English. (为避免用he or she, his or her )
eg. Everybody started waving their flags (正式用 his or her flag).
Everybody can do it if they try( 正式用 if he or she tries)
B. 在疑问尾句中如：Everybody has arrived, haven't they?
例一中,请注意flag的数,用了their, 用复数,而用了his or her则用flag 而hair在这里作不可数名词,不存在这个问题.所以原句中,如有his or her, 则选它（比较正式）,男女都没意见,或选their.（大家都认可）
而这个every boy and (every ) girl 中既然出现了girl 一词,再用his,显然不是最好,尤其是女权运动方兴未艾的现在.
所以我认为最佳答案应为D.
补充：我怀疑此题是没有改编好的一道题.它的前身是：
Every boy and girl must have ____uniform neatly kept.
A.his. B.her C.their D.them.
请注意这里的uniform没有用复数uniforms, 女同胞们,对不住了,为了语法正确,只好选A了,这是祖辈们都这么用,没办法,要怪就怪出题者.（其实此题还有不妥,应是keep one's uniform neat的被动式：have one's unform kept neat. 而不是keep one's uniform neatly 或neatly keep one's uniform )
没改好的另一个原因：现在大多数男孩都是平头,甚至是女孩子都这样,不用comb其hair 也很neat!