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问题 计算题

一辆小汽车通过长1100米的隧道，小汽车刚进隧道时的速度是10m/s，出隧道时的速度是12m/s，(小汽车可看成质点)求：

小题1:小汽车过隧道时的加速度是多大？

小题2:通过隧道所用的时间是多少？

答案

小题1:

小题2:

（1）                                    4 分

                      3分

（2）                                   4 分

                                       3分

填空题

Beijing: The United States and North Korea had their first (1) in four months here this afternoon as part of the (2) negotiations on how to end North Korea’s nuclear program, but diplomats played clown prospects for (3) . The talks are at the Diaoyutai (4) , a sprawling, garden-filled (5) in western Beijing, with negotiators gathering around a giant hexagonal table built to (6) the six delegations. The Chinese placed the Americans and the North Koreans in (7) , which may have facilitated the (8) between Mr. Kelly and Mr. Kim, which took place (9) in the afternoon session. The two spoke for 30 minutes, two Asian diplomats (10) . The early indications of how the talks are going (11) . A South Korean who took part in the meetings described North Korea as "willing to (12) through dialogue." Chinese officials also put a (13) on the talks. "I heard talks this morning and this afternoon were very successful," the Foreign Minister, Li Zhaoxing, told delegates (14) . But Japanese and Russian participants were (15) . The Russian (16) , Aleksandr Losyukov, described the negotiations as (17) . "So far, the countries have put forward a number of (18) , which are (19) the development of these talks," he told Russian reporters in Beijing. "I would not say that I am feeling (20) ."
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单项选择题

风险的表现具有( )，需要层层剖析，才能深入到最基本的风险单元，以明确风险的根本来源。

A．相对性

B．多样性

C．阶段性

D．层次性
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