问题

Max often ______our books and pens ______the floor, when he ______our desks.
A:knocks, onto; walks past
B:knock, onto; walks passed
C:knocks, off; walks past
D:knocks, off; walks passed;
B:knock, onto; walks passed
C:knocks, off; walks past
D:knocks, off; walks passed;
正确答案是: