命题“若x>0,则x2>0”的否命题是______命题.(填“真”或“假”之一)
命题“若x>0,则x2>0”的否命题是:若x≤0,则x2≤0,显然为假命题.
故答案为假.
It was surprising ______ most people paid more than 100 dollars just to see that famous star.
A.which
B.that
C.whether
D.where
当开大或关小泵出口阀的开度时,()不变。
A.管路特性曲线
B.泵的特性曲线
C.工作点
D.泵的效率