为防止食品腐败变质,一般采取的保存方法有( )
①高温 ②低温 ③保持干燥 ④保持湿润 ⑤暴露空气中 ⑥隔绝空气.
A:①③⑤
B:①④⑤
C:②④⑥
D:②③⑥
It's________of him to set his aim high but do little,so he is always leaving things undone.
北美洲地形、地势特点与亚洲不同,可概括为( )