希腊文明勃兴的因素中最重要的客观条件是（  ）

(B)

Li Qiang and Li Gang are brothers. But their living habits (习惯) are different. Now let’s go to Li Qiang’s room. Li Qiang cleans his bedroom every day and puts his things away. Look! There is a computer on the desk. There are two balls under the bed. A guitar and a kite are on the wall. Some books are on the shelf. So he must be a careful (细心的) boy. Now let’s go to Li Gang’s room. The room is not clean. Can we see his clothes on the desk? Oh, yes. We can see a football and a knife on the desk, too. Li Gang never does any cleaning on weekends. So his room is in a mess.

What do you think of Li Qiang and Li Gang? Li Qiang is a good boy. Li Gang must learn from his brother.