Nowadays, thr ar mor and mor __ _ in __ _. It is stimatd that ___. Why hav thr bn so many ____? Mayb th rasons can b listd as follows.Th first on is ______. Bsids,_____. Th third on is _____. To sum up, th main caus of it is du to _____. It is high tim that somthing wr don upon it. For on thing,_____. For anothr thing, _____. All ths masurs will crtainly rduc th numbr of _____.