A:将气体点燃
B:将气体通过足量澄清石灰水中
C:将气体通过灼热的氧化铜
D:将一氧化碳倒出
连线。
①frog____ A. It's small and yellow.
②chick____ B. It's small and green.
③cow____ C. It's black and white.