These learning strategies mainly aim at foreign languages study, including English.
单项选择题Americans used ______ gallons of water each day in 1980.
单项选择题Noise below the level of 85 decibels ______.
单项选择题Ⅰ. 完形填空 Close 阅读下列短文,从每小题所给的A、B、C、D四个选项中选出一个最佳选项。
单项选择题Air pollution is caused by ______.