just as we were teaving,the postmon(knoked\was knocking)at the door选择括号内的

just as we were teaving,the postmon(knoked\was knocking)at the door选择括号内的
just as we were teaving,the postmon(knoked\was knocking)at the door
选择括号内的

just as we were teaving,the postmon(knoked\was knocking)at the door选择括号内的
Just as we were leaving,the postman knocked at the door.[正当我们要离开时,邮递员敲门了.]
knock是短暂性动词,用一般过去时,而不用过去进行时.

knocked