螺纹按顺时针旋进者为左旋。
参考答案：错
—Could you help me to carry the heavy desk? I can't do it alone.
—________. [ ]
A. I'm OK.
B. My pleasure.
C. You're welcome.
D. With pleasure.
竖直向上抛出的小球运动中受到大小不变的空气阻力F的作用，最高点距抛出点的距离为H，则从抛出到落回抛出点的过程中，空气阻力对小球做的功为（ ）
A．-2FH
B．-FH
C．FH
D．0
the heavy desk? I can't do it alone.