Learning to write is learning to think. You don’t know things clearly _________ you can writethem down.

In summer, food goes bad easily     the weather is very hot.

Because of the heavy traffic, it was already time for lunch break         she got to her office.

 In a position like this, one can ________  stand up _______ lie down . So it is very uncomfortable.

 Daisy has been learning Putonghua __________ the age of five.