I ________ an invitation to the concert. I can't wait to go.( )
A.receiveB.will receive
C.was receivingD.have received
已知实数a,b,则“”是“”的()
平行线和的距离是()
命题“”的否定是()
.已知二次函数满足且,那么它的图象是下图中的())
函数的图象是()