You must turn off the gas after cooking. You can never be ______ careful withthat.

---- Do you think it's a good idea to make friends with your students? ---- _____ , I do．I think it's a great idea．

As is known to all language learners, newly learnt words will soon be forgotten unless ______ used in everyday communication.

It is generally believed that a successful Olympic Games            relies on well-performed IT services.

 When we got there, he was about to leave, so he only had time to explain _____ to us what he thought of our plan.