---Mum, it’s late. Why are you still here?

---Dad hasn’t come back yet. I _____ for him.

A．am waiting

B．have waited

C．was waiting

D．waited

若有定义：int x=1，y=2；float a=3.7，b=2.1；则(x+y)%2+(int)a/(int)b表达式的值为______。