液压校直机是利用液体压力加压于工件来校正工件的变形。()
参考答案:对
Tim has to _____ the guitar every day. [ ]
A. practice
B. practices
C. practising
基数效用论的基本假设条件有()
A.效用是可以衡量的
B.MU递减
C.MRCSxy递减
D.货币边际效用不变