昆虫能分泌信息素。下列是一种信息素的结构简式，下列说法正确的是（）。 A.这种信息素 发布时间：2017-07-20 13:59 │ 来源：www.tikuol.com 题型：单项选择题 问题： 昆虫能分泌信息素。下列是一种信息素的结构简式，下列说法正确的是（）。A.这种信息素不可以与溴发生加成反应B.它可以发生银镜反应C.它只能与发生反应D.它是乙烯的同系物
题型：单项选择题 Task-based Reading. Louis Braille was born in Coupvray, France. He was a very small child. Unluckily, at the age of four, he became blind by accident. Louis began attending school in his town when he was seven years old. Three years later, Louis and his father traveled to Paris. There, he went to a school for blind children. One day a French soldier, Charles Barbier, visited the school. Barbier invented a system of night-reading. This system used small dots for the letters. Soldiers used this system in time of war. Barbier thought this system could help the blind to read. Soon Braille discovered that there were some shortcoming (缺点) in Barbier's system, but it gave Louis a brilliant idea. He improved Barbier's system. By the age of fifteen, his new system was completed! Now he wanted blind schools to try his system. Luck went against him again. The school refused to use his system. Louis died in 1852 in Paris at the age of forty-three. Two years after he died, the blind schools began to use his system. Today we call this system Braille in honour of Louis Braille. His system is used for all languages, and for maths, science, writing, music, and computers for the blind. Louis BrailleTimePlaceEventsin ________ (1)in Coupvraywas bornat the age of four/became ________(2)at the age of sevenin ________ (3)started schoolat the age of ________ (79)at the age of ________ (4)studied in a school for blind childrenby the age of 15/completed his new systemin 1852in Paris_________(5) 查看答案
题型：单项选择题 近日，曾经风暴一时的呼拉圈又走进群众的业余生活，但有专家以为，转呼拉圈运动量不大，难以达到运动效果，而且易造成不良后果。以下哪项如果为真，最能支持上述观点？A．呼拉圈运动简便易行B．转呼拉圈容易造成腰肌劳损C．喜爱呼拉圈运动的人越来越少D．延长转呼拉圈时间可提高运动效果。 查看答案
，下列说法正确的是（）。
发生反应，下列说法正确的是（）。发生反应