-- Lots of trees and flowers _______on both sides of Huanshan Road last year.
-- Oh, that's beautiful.
A:are planted
B:were planting
C:were planted
D:have planted
①社会文明进步
②经济繁荣昌盛
③生命受到尊重
④行人不受约束
在一定条件下,分别以高锰酸钾、氯酸钾、过氧化氢(H2O2)为原料制取氧气,当制得同温、同压下相同体积的O2时,三个反应中转移的电子数之比为 ( )