问题
单项选择题
口腔细菌种类复杂的主要原因是
A．适宜的温度
B．适宜的pH值
C．丰富的营养
D．不同的Eh
E．唾液成分多样化
答案
参考答案：C
解析：口腔中的各种食物和唾液为各种细菌提供了丰富的营养，再加上口腔中适宜的温度、湿度及各种类型的软硬组织提供了复杂的生态环境，适宜于细菌生长。
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口腔细菌种类复杂的主要原因是
A．适宜的温度
B．适宜的pH值
C．丰富的营养
D．不同的Eh
E．唾液成分多样化
参考答案：C
解析：口腔中的各种食物和唾液为各种细菌提供了丰富的营养，再加上口腔中适宜的温度、湿度及各种类型的软硬组织提供了复杂的生态环境，适宜于细菌生长。
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| Here is a story about a clever dog. It. was a guide dog. A guide dog can help blind people walk along the streets and do many other things. One day a guide dog and a blind man 1 on a bus together. The bus was 2 of people and there were 3 vacant (空的) seats. Soon one man stood up and left his seat. The dog 4 the blind man to the seat, but there was 5 space for both of them. The dog began to push the people on each side with his nose. He pushed and pushed 6 the people moved and finally there was enough space for 7 people. The blind man then sat down and the 8 got up on the seat at his side. The dog lay down and put his head on the blind man's lap. He was very comfortable and soon fell a sleep. Every one on the 9 couldn't help 10 at the dog. | ||||
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