用custom,habit, practice和usage填空,并把句子翻译成汉语。
①It is a good _________to eat and sleep regularly.
翻译:_________________________________________________
②Social________ vary in different parts of the world.
翻译:_________________________________________________
③It's his _________to furnish references to all his quotations.
翻译:________________________________________________
④_________determines what is good English.
翻译:________________________________________________
