— Why does the river smell terrible? — Because large quantities of polluted water _______ into it.
Eating too much fat can _______ heart disease and cause high blood pressure.
--- Tom, why didn’t you come to the meeting yesterday? --- I _____, but my car broke down.
There is no doubt ______ man will conquer nature some day.
______ different life today is from ____ it was 20 years ago.
Paper-making began in China and from here it ________ to North Africa and Europe.