题目

已知命题p1：存在x0∈R，使得x＋x0＋1<0成立；p2：对任意x∈[1,2]，x2－1≥0.以下命题为真命题的是( ) A．(綈p1)∧(綈p2)                 B．p1∨(綈p2) C．(綈p1)∧p2                     D．p1∧p2 答案：C ∵方程x＋x0＋1＝0的判别式Δ＝12－4＝－3<0， ∴x＋x0＋1<0无解，故命题p1为假命题， 綈p1为真命题； 由x2－1≥0，得x≥1或x≤－1. ∴对任意x∈[1,2]，x2－1≥0，故命题p2为真命题，綈p2为假命题． ∵綈p1为真命题，p2为真命题， ∴(綈p1)∧p2为真命题，选C.       Maybe ten-year-old Elizabeth put it best when she said to her father,“But, Dad, you can't be healthy if you're dead.”      Dad, in a hurry to get home before dark so he could go for a run, had forgotten to wear his safety belt -- a mistake 75% of US population make every day. The big question is why.      There have been many myths about safety belt ever since their first appearance in cars some forty years ago. The following are three of the most common.      Myth Number One: It's best to be“thrown clear”of a serious accident.      Truth: Sorry, but any accident serious enough to “throw you clear" is able going to be serious enough to give you a very bad landing. And chances are you'll have traveled through a windshield (挡风玻璃) or door to do it. Studies show that chances of dying after a car accident are twenty-five times in cases where people are “thrown clear”.      Myth Number Two: Safety-bets “trap”people in cars that are burning or sinking in water.      Truth: Sorry again, but studies show that people knocked unconscious (昏迷) due to not wearing safety belts have a greater chance of dying in these accidents. People wearing safety belts are usually protected to the point of having a clear head to free themselves from such dangerous situation, not to be trapped in them.      Myth Number Three: Safety belts aren't needed at speeds of less than 30 miles per hour (mph).      Truth : When two cars traveling at 30 mph hit each other, an unbelted driver would meet the windshield with a force equal to diving headfirst into the ground from a height of 10 metres. 62. Why did Elizabeth say to her father,“But, Dad, you can't be healthy if you're dead”? A. He was driving at great speed.                       B. He was running across the street. C. He didn't have his safety belt on.                    D. He didn't take his medicine on time. 63. The reason father was in a hurry to get home was that he _______. A. wasn't feeling very well                              B. hated to drive in the dark C. wanted to take some exercise                        D. didn't want to be caught by the people 64. According to the text, to be “thrown clear" of a serious accident is very dangerous because you _______. A. may be knocked down by other cars               B. may get serious hurt thrown out of the car C. may find it impossible to get away from the seat D. may get caught in the car door 65. Some people prefer to drive without wearing a safety belt because they believe _______. A. the belt prevents them from escaping in an accident B. they will be unable to think clearly in an accident C. they will be caught when help comes              D. cars catch fire easily 66. What is the advice given in the test? A. Never drive faster than 30 miles an hour.        B. Try your best to save yourself in a car accident. C. Never forget to wear the safety belt while driving. D. Drive slowly while you're not wearing a safety belt.