— Did Eric go swimming yesterday? — _________. He went to the movies with Mark.
A：Yes, he did
B：Yes, he does
C：No, he didn't
D：No, he doesn't
We don't think it's good to stay_____ late to play computer games.
判断对错．
两条直线相交组成的4个角中如果有一个角是直角，那么其他3个角也是直角．
____
质量m=2kg的物体静止在水平地面上，它与地面间的动摩擦因数μ=0.4，一个F=10N水平恒力作用在物体上，使物体在水平地面上运动．F作用4s后撤除．（取g=10m/s2）则：
