实施多元化经营战略的形式有（）
A.纵横多元化
B.纵向多元化
C.水平多元化
D.多向多元化
参考答案：B, C, D
循环流化床锅炉空气预热器漏风的原因有哪些？
When father was young, he（）from morning till night.
A.was made work
B.was made working
C.made to work
D.was made to work
