Understanding the cultural habits of another nation，especially ________containing as many different cultures as America，is a difficult thing.

The doctor thought ____ would be good for you to have a holiday.

____ child is pleased, for____ of them has got his own share. 

Many people have been ill with a strange disease these days, _______ we’d never heard of before.

 When ___ comes to saving energy , big changes start with small steps , like turning off the lights.