-- Miss Wang, I'm sorry I am late because I _______ to catch the early bus.
-- It doesn't matter. You'd better come to school earlier next time.
A：needed
B：failed
C：managed
一重为20N的物体，它受到的重力与它的质量的比值为____，当它的质量增大两倍时，它的重力与质量的比值为____。
