板式换热器特点是（）。
A.传热效率高
B.适应性差
C.不能精确控制换热温度
D.占地面积大
参考答案：A
The teacher _____ some old friends on his vacation trip to Paris.[ ]
A. dropped by
B. dropped in
C. droped by
D. droped in
征占用多大的林地面积必须由国务院林业主管部门审核？
