近年来，我国许多城市禁止汽车使用含铅汽油，其主要原因是[ ]
A．提高汽油的燃烧效率
B．降低汽油成本
C．避免铅污染大气
D．铅资源短缺
答案：C
China’s population is expected to increase to about 1.5 billion, ____ it will start to decline slowly.
A．after that
B．since when
C．on which
D．after which
传统的离散型车间作业按生产工票下达生产命令，而JIT作业管理采用按生产率安排生产计划。
