题干

下列关于真核生物、原核生物和病毒的叙述中有几项正确(  )

①乳酸菌、青霉菌、大肠杆菌都属于原核生物

②乳酸菌、酵母菌都含有核糖体和DNA

③T2噬菌体中只有一种细胞器,即核糖体

④细胞没有叶绿体就不能进行光合作用

⑤有些细菌只含有RNA.

A:1项

B:2项

C:3项

D:4项

上一题 下一题 0.0难度 选择题 更新时间:2019-09-18 08:11:19

答案(点此获取答案解析)

A

同类题2

一辆载满20t电石的挂车,在浙江滨江区燃起熊熊大火并伴有大量黑烟。事故路面上洒落了五六百米燃着的石头。这辆货车在雨中整整燃烧了一天,消防官兵对大火也束手无措,场面让人震撼。大家对电石的化学性质产生了浓厚的兴趣,请你一起与他们完成下列探究活动.

【查阅资料】电石的主要成分是碳化钙(CaC2),可以与水反应生成一种可燃性气体及白色固体。常见的可燃性气体中,乙炔(C2H2)燃烧时伴有大量黑烟。

【猜想与假设】

电石与水反应生成的可燃性气体是:氧气、氢气或乙炔(C2H2);同学们做出以上猜想的依据是____,大家讨论后,一致认为该气体不可能是氧气,原因是____。电石与水反应生成的白色固体是:氧化钙、氢氧化钙或碳酸钙中的一种。同学们经过讨论认为白色固体不可能是氧化钙,因为氧化钙会与水反应。

【实验探究】

实验步骤

实验现象

实验结论

⑴取适量电石加水反应,收集生成的气体,验纯后点燃.

气体燃烧,产生黄色火焰并伴有浓烈黑烟.

电石与水反应产生的气体是____

⑵取适量反应后生成的固体于试管中,滴加过量稀盐酸.

固体溶解,____


电石与水反应产生的固体不是碳酸钙

⑶取适量反应后生成的固体于试管中加水,向上层清液中滴加____

溶液变红

电石与水反应产生的固体是氢氧化钙

【反思交流】请根据以上实验结论写出电石与水的反应的化学方程式____

载有电石货车可以在雨中整整燃烧一天而不熄灭,说明电石与水反应是____(填“吸热”或“放热”)反应。

同类题3

阅读理解

          The ground we walk on seems firm, but deep under the earth and under the sea the rocks change and move. In some parts of the world there are “fire mountains”, which we call volcanoes. From time to time they burst open and throw out fire and burning ashes. These volcanoes are very dangerous.

          Hong Kong does not have any volcanoes but there are many volcanoes in Indonesia and Philippines. There is also a famous mountain near Tokyo, Japan, which is a volcano too. Its name is Mount Fuji. For much of the year,it is covered with snow.

          One of the most famous volcanoes which erupted in recent times was Krakatoa, on an island in Indonesia. The first explosions took place on 20th May, 1883, but the biggest eruption did not come until the 26th and 27th August of that year. The people on the island were used to the explosions by that time, and so they were completely unprepared for this terrible happening. Almost all the people on the island died and the explosion also made huge waves in the sea, which drowned (淹死) many people on the other island nearby. After the eruption was over,people saw that the whole northern part of the island had completely disappeared. Scientists say that 15 cubic (立方) kilometres of rocks and ash were thrown up in the explosion. The noise of the explosion was heard nearly 5,000 kilometres away in the middle of the Indian Ocean,and the city of Jakarta was completely dark for about two and a half hours.