从分别标有数字1、2、3、4的四张卡片中,一次同时抽2张,其和为奇数的概率是( )。
对机床的辅助装置(如送料、夹紧),液压泵通常优选()。
A.齿轮泵
B.柱塞泵
C.螺杆泵
D.叶片泵
Is monopolistic competition a market in which: each seller produces a differentiated product compete on price, quality, marketing()①A. No No ②B. No Yes ③C. Yes Yes
A. ①
B. ②
C. ③