请问knock的过去式是什么呀?

knock的过去式=knocked
名词 n.
1.短促的敲打(声)
When he heard the knock, he ceased writing.
当他听到敲门声, 就停下来不写了.
2.爆震声
3.敲击声；敲门（或窗等）声
及物动词 vt. & 不及物动词 vi.
1.敲, 击, 打
Please knock before entering.
进来前先敲门.
The children were knocking the bottom of the box.
孩子们在敲箱子底.
及物动词 vt.
1.批评, 数落, 非难
The newspapers are too fond of knocking the team.
报纸专爱挖苦那个队.
2.把…撞击成（某种状态）
3.（心）怦怦跳；（膝盖）打哆嗦
4.（尤指因故障）发碰撞声,嘭嘭作响
5.打,凿（洞）
hear的过去式=heard
及物动词 vt. & 不及物动词 vi.
1.听到, 听见
The deaf do not hear at all.
聋子根本听不见声音.
I hear the door open.
我听到门开了.
I often hear him singing.
我常听见他唱歌.
I heard my name called.
我听到有人叫我的名字.
及物动词 vt.
1.听说, 得知
We've heard that you would graduate soon.
我们听说你很快就要毕业了.
Have you heard why she did so?
你听说过她为什么要这么干吗?
2.听取; 审理