Economy should be developed to raise people’s living standard. , effective measures should be taken to deal with different types of pollution caused by the economic development.
___ is left over may be put into the refrigerator, ____ it will keep for two or three weeks.
Modern science has given clear evidence ____ smoking can lead to many diseases.
Three young men have been arrested because they were caught ___ an old lady last night.
______ a little earlier, you could have got a copy of his latest book.
Don't be afraid to ____ help if you have any further problems.