下列方法或做法不能用来鉴别CO2和CO的是（）
I still consider Jack as one of my best friends though ______ he did caused some ______ to his fame.
我国太阳能最丰富的地区是（ ）
如图，□ABCD的周长是28cm，△ABC的周长是22cm，则AC的长为（ ）
