因为hard词性为形容词和副词，非动词，因此是没有过去式和过去分词的。
hard：
adj.坚固的;坚硬的;结实的;难做的;难懂的;难以回答的;困苦的;艰苦的;艰难的。
adv.努力地;费力地;艰难地;猛力地;猛烈地;彻底认真地。
扩展资料
When I left they were all still hard at it.
我离开的时候他们都还在努力工作。
You think youre really hard, dont you?
你是不是以为自己真的很勇猛？
Come and get me if you think youre hard enough.
你要是觉得自己有种，就冲着我来吧。
Her show now has a hard political edge to it.
她现在的表演具有强烈的`政治性。
Their success was the result of years of hard graft.
他们的成功是多年艰苦奋斗的结果。
