搜题请搜索小程序“爱下问搜题”
问题 选择题

在巴斯德曲颈瓶实验中，甲瓶的瓶口是竖直向上；乙瓶的瓶口是拉长呈S型的曲颈；将两个烧瓶内的肉汤同时煮沸放凉后，观察肉汤的变化。本实验的实验变量是

[ ]

A．氧气的有无

B．烧瓶放置时问的长短

C．微生物的有无

D．烧瓶容量的大小

答案

答案：C

单项选择题

诊断肺动脉栓塞的金标准是（）

A.X线平片

B.CT肺动脉造影

C.MRI

D.X线肺动脉造影

E.超声
查看答案
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