Don’t reply to any e-mails _______ personal information, no matter how official or formal they appear.

   – Have they found out the _____ of the fire?--  Yes. It was a cigarette end that _____ the fire.

Male nurses can see things from a different angle than women and bring a male way of thinking _____problems.

Nowadays, many people walk to work ________ Copenhagen Conference calling for living a low-carbon lifestyle to deal with global warming.

Despite the fact that Jack has lived in USA for many years，he finds it no easy to _____himself to its culture and customs.