An increased concentration of carbon dioxide and certain other gases in the Earth’s atmosphere ______ global warming.

.— Sorry, I _______ to buy the book you need for you.— Never mind_______ it myself after school

There are a lot of of bike riding.—I agree. It’s good for the environment and it saves money.

The Smiths have gone to New York for their holiday, with an old servant ____ their house.

Most of the developing countries are faced with lots of troubles , _____the financial problem is not the worst