第二节:完形填空(共20小题;每小题1分,满分20分) 阅读下面短文,掌握其大意,然后从36~55各题所给的四个选项(A、B、C和D)中,选出最佳选项。 There are many different ways of seeing a town for the first time. One of them is to walk around it, guide-book 36 hand. Of course, we may 37 with our guide-books the history and 38 development of a town and get to know them. 39 then, if we take our time and 40 in a town for a while, we may get to know it better. When we 41 it as a whole, we begin(2003?常州)右图是常用的实验室制取气体的发生装置.据图回答下列相关问题.(1)制取O2时,A中应放二氧化锰二氧化锰,其作用是加快H2O2的分解速率加快H2O2的分解速率.(2)制取H2时,B中可放稀盐酸或稀硫酸稀盐酸或稀硫酸.(3)制取CO2时,反应的化学方程式为CaCO3+2HCl=CaCl2+CO2↑+H2OCaCO3+2HCl=CaCl2+CO2↑+H2O.(4)在上述三种气体中,能用向下排空气法收集的是氢气氢气.