题目

等腰三角形一边长为4,一边长为9,它的周长为_______,面积为_________. 答案：22;2 —It’s reported that PM2.5 pollution is the main problem ________ air pollution today.— And I also know according________ the research the number of ‘foggy’ days in Beijing is reducing.A.in, toB.by, inC.with, toD.at, at