乘客携带大型行李时，可以额外加收运输费用。
参考答案：错
I usually sit _____ the classroom, so that I can hear the teacher who likes to stand _____ the class clearly. [ ]
A. in front of; in the front of
B. in the front of; in front of
C. in front of; in front of
D. in the front of; in the front of
物质由______态变成______态的过程叫做升华；物质由______态变成______态的过程叫做凝华．升华过程______热，凝华过程______热．
