1 . Thirty percent of air in the city ________ (pollute) so far. (所给词的适当形式填空)

2 . Chen Wei, a high school student in Beijing, had his dinner ________________ (interrupt) when he heard someone ________________ (scream) from another table. (所给词的适当形式填空)

3 . ________________ (distinguish) for its attractive scenery, Hangzhou witnesses large numbers of tourists every year. (所给词的适当形式填空)