【判断题】The central theme of a paragraph is usually summarized in what is called the topic sentence. It often appears at the end of the paragraph; however,it may also be found in the middle or at the beginnin...
【多选题】硫化氢的主要来源有()。
B.
天然气或原油中的有机物在化学反应或微生物作用下能分解产生硫化氢
D.
含硫的矿石(如硫化亚铁FeS)与酸接触产生H 2 S
【简答题】资产阶级维新派自身弱点和局限的主要变现是什么?
【判断题】The theme of a send-off or farewell party or dinner is usually related to past events instead of showing resolutions or hopes for the future.
【简答题】实验室制取乙烯的装置如右图所示,请回答: (1)反应中浓硫酸起 剂和 剂的作用。 (2)该实验可能产生的主要有机副产物是 。(写名称) (3)制取乙烯的反应的化学方程式是: 。