Her father told her to be careful when _____ the street.  

A．he is crossing

B．she is crossing

C．crossed

D．crossing

若某个国家突然增加了大量可以调动的资源，AS曲线会发生什么变化？（）

A.向左旋转

B.向右平移

C.向左平移

D.向右旋转