-- Excuse me. where are we going to have our class meeting?
-- I’m not sure. Ask our monitor, please. He know.
A:can
B:may
C:need
D:shall
炎帝和黄帝部落主要活动于( )
—It's ________ the desk.
夏商西周社会以____亲疏关系区分尊卑等级。西周时,周王以下的____、____、____是享有各种特权的贵族。
a和b为质量相等的两份固体,a为氯酸钾,b为混有二氧化锰的氯酸钾.分别同时加热a和b至完全反应,下列图象能正确表示氧气的质量随时间变化关系的是( )