Courtesy is as important in speaking over the phone as in talking to people face to face. Therefore , it is essential to know the etiquette of calling, especially in the business environment . essential :
A.
worthless
B.
nice
C.
important
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参考答案:
举一反三
【多选题】如图所示,在 M 点分别以不同的速度将两个小球水平抛出,两小球分别 落在水平地面上的 P 点、Q 点.已知 O 点是 M 点在地面上的竖直投影, OP : PQ = 1 : 3 ,且不考虑空气阻力的影响,下列说法中正确的是