David, could you tell me ______ —Every four years.

It is acknowledged that ___ shortest distance between persons is ___ sincere smile..

下列各项句子中“之”字意义与用法不相同的一组是（ ）

What kind of person do you want to helpyou—______ always trying his best and nevergiving up in time of difficulty

Many died or returned home, but most remained in California to________a life for themselves in the new towns or on farms.[ ]