在①丙烯 ②氯乙烯 ③苯 ④甲苯四种有机化合物中,分子内所有原子均在同一平面的是[ ]
A.①②
B.②③
C.③④
D.②④
答案:B
Earned value technique is used in which process
A) Direct and manage project execution. B) Monitor and control project work. C) Integrated change control. D) Develop project management plan.
万用表的表头是一个( )测量机构。
A.电磁式
B.磁电式
C.电动式
D.感应式