本来就有单数词性的：anybody, anyone, everybody, everyone, nobody, no one, somebody, someone。

问题在于在下文使用代词时无法确定使用he还是she。

目前：

-在口语中，可用they指代anybody, everybody, somebody, etc.

-在正式书面语中：

（1）如可确定性别，则用he/him 或是 she/her

（2）如不确定性别，则用 "he or she"

（3）重写句子以避免此问题：

·变单数为复数：When someone studies, he can learn a lot. --> When people study, they can learn a lot.

·用you改写句子：When you study, you can learn a lot.

·去掉代词：Studying is a good way to learn a lot.