________in the computer games,the boy no longer put his heart into study.
Johnny, you ______ play with the knife; you _____ hurt yourself.
Since 1949, the peoples living standard _______, causing a big _______ in population.
______ has already been pointed out, grammar is not a set of dead rules.
There is a mountain ________ the top is always covered with snow.
---Why did the police _____ the crowd?---Because the presidents car ____ in the street.