命题:“若A∪B=A,则A∩B=B”的否命题是______.
“若A∪B=A,则A∩B=B”的否命题:
“若A∪B≠A则A∩B≠B”
故答案为:若A∪B≠A则A∩B≠B.
–Excuse me, sir, but I don’t think you can smoke here.
–Really sorry. I ______ this is a non-smoking area.
A.don’t know
B.didn’t know
C.have no idea
D.haven’t known
动力粘度的概念是什么?