Tom and his sister ______ to the barbecue last Saturday.They were very happy.
A:have invited
B:were invited
C:were inviting
D:invited
如果执行图的程序框图,那么输出的S=( )
如图是一辆汽车做直线运动的s-t图象,对相应的线段所表示的运动,下列说法中不正确的是( )