具体计划
参考答案：
是指有明确规定的目标和一套可实行的操作方案。
—How does Meimei go to school?
—She ________ a bus, but now she walks to school.
A. used to take
B. is used to take
C. is used to taking
D. used to taking
产业市场需求的特点有（）。
A、替代性
B、派生性
C、伸缩性
D、波动性
