Everybody has expressed their determination.每个人都表过决心了。
不定代词everybody/everyone/anybody/anyone/somebody/someone/nobody/no one等总是被看作单数。它们做主语时，谓语动词要用单数形式。因此，正式文体里，指代这些不定代词的人称代词、物主代词也用his/him等单数形式。
If anybody comes, ask him to leave his address.如果有人来，请他留下地址。
解析
很多以they/them/their/themselves代替he/him/his/himself来指代单数性的everybody等不定代词是一种奇特语言现象。有时普遍用he/him/his等因为这时的he/him/his并不专指男性。
