液态生长有什么优缺点？
参考答案：
最简单最廉价但其外延层的质量不高
词义替换
Pandas are becoming less and less in recent(近来) years.
A．more and more
B．few and fewer
C．fewer and fewer
D．better and better
光线垂直射到镜面上时，反射角是______．入射光线与反射光线的夹角是______．
