Many people think they have to spend a lot of money to keep healthy. Leading a healthy lifestyle doesn't have to cost much,         . 

He speaks English well indeed, but of course not___________a native speaker.

____ the fire broke out, three fire-engines were rushed to the spot.

 ---I was riding along the street and all of a sudden, a car cut in and knocked me down. ---You can never be         careful in the street.

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