A:
B:
C:
D:
— Why are you so ________?
— I am watching an ________ basketball game.
在Rt△ABC中,∠C=90°,AB=13,AC=12,则sinB的值是
— Bob, shall we go and meet our new classmate?
— Sorry, I'm busy now. But you ________ ask David to go with you. He is free.
请从4a2,(x+y)2,1,9b2中,任选两式做差得到的一个式子进行因式分解是____