Our teacher wasn’t blaming anyone ; he _______ said errors like this could be avoided．

Chemical pollution will bring about a threat to agriculture and food chain, and ________ to human health.

As is known to all, the newly learnt words will soon be forgotten unless_____ used in everyday communication.

 ---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.

Jack has a good habit of keeping a diary every day;      he is very good at writing.