下列四个命题中，假命题为（）

题干

下列四个命题中，假命题为（）

A： $\exists x \in R$ ，使 $l g x > 0$ 成立

B： $\exists x \in R$ ，使 $x^{\frac{1}{2}} = 2$ 成立

C： $\forall x \in R$ ， $2^{x} > 0$ 均成立

D： $\forall x \in R$ ， $x^{2} + 3 x + 1 > 0$ 均成立

上一题下一题 0.0难度选择题更新时间:2012-10-30 08:21:08

D

根据材料内容选择最佳答案。

Wanted Are you hard-working? Do you like to meet people? If your answer is "Yes"; then we have a job for you as a waiter. Call AL Hotel at 5564779!	Summer Job Do you like to talk with people? Do you like to write Stories? If you want to work for our magic as a reporter, please call Karen at 5583366.
Help Wanted Do you like babies? Can you look after a baby for two days? If you are sure to take good care of it, call Mr. Green at 7665898. $80 or more. Today! Be quick	Cleaner wanted Can you make a large house clean and tidy? If you hope to get paid $20 once, call us this evening from 18:00 to 20:00. Our telephone number is 6338001.