C-14-Q029mediumsingle_mcqIn △ABC\triangle ABC△ABC, DE∥BCDE \parallel BCDE∥BC, AD:DB=2:3AD:DB = 2:3AD:DB=2:3. Then AE:EC=?AE:EC = ?AE:EC=?a3:23:23:2b2:32:32:3c2:52:5