气温为23℃时，某河段溶解氧浓度为4.5mg/L，已知该河段属于Ⅱ类水体，如采用单项指数法评价，其指数为( )。(根据《地表水环境质量标准》，Ⅱ类水体溶解氧标准为不小于6mg/L)

A．0.75

B．1.58

C．2.66

D．3.25

句型转换。

1. Can I help you? (同义句)

    _______ can I _______ you?

2. How much is the apple? (同义句)

   What's the _______ _______ the apple?

3. I like comedies best. (就划线部分提问)

    ___________________________________?

4. He wants to be a teacher. (就划线部分提问)

    ___________________________________? 

5. The price of the shoes is 15 yuan. (同义句)

    The _______ _______ 15 yuan.