Specimen可与sample换用，但常指人或物中选出的有代表性部分，或指供科研、化验或检验用的标本。 主要内容如下:分 析介绍了几种常见抽油泵的工作原理、构造 、 适用范围及分类. The newest congressional report acknowledges the crucial worth of technical education, but also asserts the review of the humanities (人文学科)and social sciences have to keep on being central elements of The usa's instruc... https://housegurgaon.news.blog/