A:always watch
B:too small a car
C:have always watched
D:have always been watching
谨食之,时而献焉。退而甘食其土之有,以尽吾齿。盖一岁之犯死者二焉;其余,则熙熙而乐。岂若吾乡邻之旦旦有是哉!
作者写蒋氏这番话,主要是为了说明( )