A:则
B:,则
C:,则
D:,则
甲、乙、丙三个集气瓶中,分别盛有空气、氮气和氧气,用一根燃着的木条分别插入瓶中,依次观察到火焰熄灭、继续燃烧、燃烧更旺,则瓶中所盛气体分别是( )
关于我国位置的说法,正确的是( )
What's the _______ of having a public open space where you can't eat, drink or even simply hang out for a while?