Jack was born ___________ May 5th, 1980.[ ]
A. in
B. at
C. on
D. /
答案:C
求实数m的取值组成的集合M,使m∈M时“p或q”为真,“p且q”为假,其中P:∀x∈R,mx2+2x+1≥0,q:∃x∈R,4x2+4(m-2)x+1=0.
下列装置操作图不能用于检查气密性的是( )