Students in our school are encouraged to ________more activities after class in order to broaden their knowledge. ( )
A:attend
B:join
C:take part
D:participate in
某实验室欲配制一定溶质质量分数的KNO3溶液,现实验室只有含少量NaCl的KNO3固体药品.
烟光、日影、露气,皆浮动于疏枝密叶之间。
一般情况下,人体最主要贮能物质是( )