（not speak） with your mouth full of food and------(be)polite.

（not speak） with your mouth full of food and------(be)polite.
（not speak） with your mouth full of food and------(be)polite.

（not speak） with your mouth full of food and------(be)polite.
Don't speak .be
这里是考祈使句的形式---动词原形开头
请及时采纳,不懂继续问( 天天在线 ）