A:由西北向东南逐渐减少
B:由西南向东北逐渐减少
C:由东南向西北逐渐减少
D:由东北向西南逐渐减少
匹____ 坡____ 文____ 象____
四____ 波____ 纹____ 像____
Although many Americans move a lot, they still________and understand each other's dialects.