However, at times this balance in nature is disturbed by human activities, _______ a number of possibly unforeseen effects.

Try to be careful. The ________you read, the fewermistakes you will make.

She is on holiday at the moment, but she’ll be back next week.

How do you find the match between Spain and Switzerland?—It’s ！ Powerful Spain lost the game by 0∶1.

Is oxygen the only gas _______ helps fire burn?