The science of computer, _____rapid progress has been made in recent years, is the most important of all science.
This new kind of chemicals will help keep the air, soil and water________ from pollution.
---I have cleaned the room three times a day. Look, It is a mess again. --- ! Wait until the children go to bed.
Not for a moment ______ sightseeing while in Europe.
He ______be lazy, but he can work hard when he feels like it.
It was early morning in London _____ Prime Minister Cameron arrived to give his speech.