Under modern conditions ,this requires varying measures of centralized control and hence the help of specialized scientists such as economists and operational research experts.

单项选择题A．which is very richB．with only more than one million populationC．which produces oilD．all the above

填空题Before Mike became an actor, what kind of school did he go to

填空题messengers

单项选择题What can you infer from the passage

单项选择题What changed Charles's life and led him into a world of natural science