命题“存在x0∈R,2x0≤0”的否定是[ ]
A.不存在x0∈R,2x0>0
B.存在x0∈R,2x0≥0
C.对任意的x∈R,2x≤0
D.对任意的x∈R,2x>0
答案:D
. You shouldn’t only trust him. You’d better the truth of the whole thing for yourself.
A.search
B.look at
C.find out
D.search for
罐液位调节系统,当调节阀装在出口管线上时,应选择()。