比较下列A,B两组句子,然后小结它们的区别

A
(1)what do you do on weekends?I often watch TV.(2)what do your friends do on weekends?They often watch TV.(3)what does he do on weekends?He often watches TV (4)what does your sister do on weekends?She often TV.
B
(1)what did you do last weekend?I watched TV (2)what did your friends do last weekend?They watched TV(3)what did he do last weekend?He watched TV(4)what did your sister do last weekend?She watched TV
（1）以上两组句子的动词都是（watch）（2）A组的句子用的是（一般现在）时,B组的句子用的是（一般过去）时；（A）组的句子有人称和数的变化,（B）组的句子却没有人称和数的变化.（3）什么是一般过去时?表示事情发生在过去的一种时态.(4)当句子中有表示过去的时间状语时,动词应该用它的（过去）式,而这种形式是怎样构成的呢?一般是动词后加ed,特殊的很多,需要自己记,如do-did,grow-grew.