搜题请搜索小程序“爱下问搜题”
问题 选择题

下列实验基本操作或实验装置正确的

答案

答案：A

B 给试管加热，应加热试管底部

C 用胶头滴管滴加液体时，滴管不能伸入到试管里面

D 长颈漏斗的颈部应伸入到液面下，防止气体从长颈漏斗中逸出。

填空题

Beijing: The United States and North Korea had their first ______ in four months here this afternoon as part of the ______ negotiations on how to end North Korea’s nuclear program, but diplomats played down prospects for______. James A. Kelly, assistant ______, and Kim Yong Ⅱ, North Korea’s deputy foreign minister, met ______ of formal discussions, ______ on direct dialogue that began after a stormy meeting ______ in which North Korea warned that it was moving quickly to ______ nuclear arms. The Bush administration had insisted ______ that it would only hold talks with North Korea ______ because, it argued, only ______ pressure would persuade North Korea to______. It got its way when North Korea dropped its insistence on ______ and agreed, after extensive efforts by China, to hold unusual simultaneous negotiations with ______,______,______ and ______ as well as the United States. Though Bush administration officials had not ______ talking privately with the North Koreans during______, the fact that Mr. Kelly and Mr. Kim met on the first day was seen as a sign of ______ by the American side.
查看答案
问答题 简答题

当潜水埋深变浅时，可能是哪些因素引起的？
查看答案