一般来说，只有当预报平均风速小于（）米/秒时，或在雷暴情况下，风向风速组中的风向应编报为VRB。
A、1
B、2
C、4
参考答案：B
—Can I tell Peter about the news?
—No, I don't want anyone else to know it. You keep it to yourself. [ ]
A. must
B. need
C. can
D. may
多项式x2+y2﹣4x+6y+28的最小值是﹙ ﹚．
