题干
--- They are quiet, aren’t they?
--- Yes．They are accustomed ____________ at meals．
--- Yes．They are accustomed ____________ at meals．
A：to talk
B：to not talk
C：to talking
D：to not talking
答案(点此获取答案解析）
D
中，点
在
上运动，给出下列四个命题：
的体积不变； ②
⊥
∥平面
； ④平面
