低氧燃烧时，产生的（）较少。
A、硫
B、二氧化硫
C、三氧化硫
参考答案：C
—_____ can we get to the Disneyland, Betty?
—Let's _____ It's much faster. [ ]
A. How; take the subway
B. How far; by subway
C. How; by subway
D. How far; take the subway
在深度为5的满二叉树中，叶子结点的个数为______。
A．32
B．31
C．16
D．15
