THE AMOUNTS OF OXYGEN AND NITROGEN IN THE AIR ALMOST ALWAYS REMAIN...

2. - DE THI THU THPT QUOC GIA NAM 2017 MON TIENG ANH TRUONG THPT QUANG XUONG 1 THANH HOA LAN 1 CO DAP AN
Tiếng Anh DE THI THU THPT QUOC GIA NAM 2017 MON TIENG ANH TRUONG THPT QUANG XUONG 1 THANH HOA LAN 1 CO DAP AN

2. The amounts of oxygen and nitrogen in the air almost always remain stable, but the amount

of water vapor vary considerably.

A. vary B. almost always C. The amount of D. stable