his parents work hard. 改为否定句 His parents don't work hard. 为什么要用don't

Question

如题所述

Answer 1

因为 His parents work had. 句子中没有 be 动词.
改为否定句时, 一般现在时, 复数用 don't ; 三单用 doesn't.
His mother works hard. => His mother doesn't work hard.
一般过去时, 用 didn't.
His parents worked hard. => His parents didn't work hard.