clear Security Summit is an initiative of Mr. Obama, considers nuclear terrorism to be one of the greatest threats to international security.

When I was young, I wanted to be________Olympic winner.

I ________ use a clock to wake me up because at six o’clock each morning the train comes by my house. (2012·新课标全国，30)

Most children feel when they work in groups than on their own.

This year red isn’t as ______ as green.