—Who's singing in the park?
—It ________ be Ann. Ann is much taller.
A:must
B:can't
C:need
D:can
意大利人在古代丝绸之路中扮演着东西文化交流使者的重要角色。错误:____ 订正:____
式子:lg5+lg2的值为( )
We felt disappointed when we found the journey was not as nice as we had e____.
物体自由下落的高度h(米)和下落时间t(秒)的关系是:在地球上大约是h=4.9t2,在月球上大约是h=0.8t2,当h=20米时,
(1)物体在地球上和在月球上自由下落的时间各是多少?
(2)物体在哪里下落得快?