Mr. Black ________ for Shanghai in a few days. Do you know when the earliest plane ________ on Sunday?

A．leaves; takes off

B．leaves; is taking off

C．is leaving; is taking off

D．is leaving; takes off

设有如下宏定义
#define MYSWAP(z，x，y)
z=x；x=y；y=z；
以下程序段通过宏调用实现变量a，b内容交换，请填空。
float a=5，b=16，c；
MYSWAP( 【7】 a，b)；