Tom eats sweet snacks but his sister eats them.
A:often, often
B:always, usually
C:never, often
D:never, never
顾炎武强调亡国与亡天下的不同:所谓亡国是“易姓改号”,所谓亡天下则是“仁义充塞,而至于率兽食人,人将相食”。这一主张( )
已知:Ⅰ.CR﹣39单体结构简式是:
Ⅱ.酯与醇有反应RCOOR′+R″OH →△催化剂 RCOOR″+R′OH(R、R′、R″代表烃基)