Mr. Li will go to Guangzhou by air. His workmates are ______ at the airport.
A:turning him off
B:seeing him off
C:taking him off
D:putting him off
783400-498000=____
346×58+56700=____
为验证人体呼出气体中含有较多的二氧化碳,先向甲、乙两试管内分别注入澄清透明的石灰水,再向甲试管的石灰水中通入空气,向乙试管的石灰水中吹入呼出气,结果是( )