when既可以和延续性动词连用,也可和非延续性动词连用.
When/while/AsIwaswalkinginthestreet,itbegantorain.
Iwascokingwhensomeoneknockedonthedoor.
WhileIwasdoingmyhomework,mymotherwaswatchingTV.
Wesangaswewalkedalong.
WhileIwasdoingmyhomework,mymotherwaswatchingTV.
When /while/Iwaswalking inthestreet,itbegantorain.
When he camein, I wasreadingthenewspaper.
Whensheheard thesadnew,shebegantocry.