命题“若a=-1，则a2=1”的否命题是______．

“有些时候文明只是十公分的宽度，有些时候只是一张纸的厚度，当我们把十公分的盲道让出来，当我们在椅子上垫一张纸……每个人的一小步就构成了我们中国文明进步的一大步。”这段话告诉我们，培育文明风尚重在[ ]

A．宣传教育、开拓创新

B．选择科学的世界观

C．脚踏实地，重在行动

D．树立崇高道德理想

压力容器进罐检验所使用的照明用电不得超过（）引入容器内的电缆应当绝缘良好，（）可靠；

某船TPC=14.1t/cm，MTC=76.2×9.81kN•m/cm，x_f=0，在xp=-28m处（）货物才能使船尾吃水减少0.35m。

A．装178t

B．卸146t

C．卸137t

D．卸163t

B

Crashing a state dinner at the White House without any invitation apparently takes a security breakdown as well as some kind of courage.

The Washington Post first reported that a couple, Tareq and Michaele Salahi, not on the official guest list, managed to slip into the state dinner at the White House on Nov. 24, 2009. The dinner was held to honor Indian Prime Minister Manmohan Singh. According to the Post, the uninvited guests had stayed in the same place with the Obamas and other important figures.

The U. S. Secret Service learned about the security breach (破坏) on Wednesday only after the couple boasted online about having attended the state dinner. One of the many photos from the dinner posted on her blog shows the couple with the smiling Vice President Joe Biden.

The White House has asked the Secret Service for a full review of what happened. “ The Secret Service is looking into its security procedures after determining that. ” Secret Service spokesman Ed Donovan said. “ An initial (初步的) finding has identified that one of our checkpoints did not follow proper procedures to ensure that the two individuals were on the invited guests list,” Donovan said. But he also said President Obama was never in any danger as well as the others at the dinner, because all the party attenders went through the security screening for weapons as there were more than three hundred people invited. “ But we do not rely on just magnetometers (检测仪) or the level of screenings, ” he added. “ That’s why we have the guards with our protectees at all times ”.

The following are more reactions to this incident:

* One senator thought authorities ought to pursue criminal charges against the couple and such behavior should be strongly discouraged.

* “ There is no need of legal help for the couple, as they just went to a party. They didn’t do anything wrong,” a lawyer expressed his opinion on this eye-catching security breach.

* Evan Botny, a current affair commentator, on Sunday said his concern was about the long-term effect on U.S. security, so it should be regarded more than a laughing matter.

* Meanwhile, a TV executive added that the couple’s attempt might be focused on money, as they

were offering interviews to networks on their experience.

45. The U. S. Secret Service got to know the incident because of _______.

A. the news from the Washington Post            

B. the announcement of some important figures

C. the couple’s boasting on the internet         

D. the report of the Secret Service spokesman

46. In paragraph 4, the spokesman thinks _______.

A. the security procedures are very efficient                     

B. such incidents could be very easily avoided   

C. the secret service needn’t be improved at all

D. the incident came as a surprise with no harm

47. According to the passage, the couple did so in order to _______.

A. enjoy a state dinner                  B. take some photos

C. become famous                     D. visit the White House

48. From the reactions, who believes the Secret Service rather than the couple is to blame?

A. A senator                                  B. A news commentator

C. A lawyer                                  D. A TV executive

下列选项不是早强剂的代号是（）

A、PA

B、AC

C、AEWR

D、RE