污染水体中的甲基汞通过食物链导致水俣病，主要是因为汞在环境中的（）A．生物降解作用

阅读理解。

     When you are reading something in English, you may often meet with a new word. What's the best

way to know it?

      You may look it up in the English-Chinese dictionary. It will tell you a lot about the word: the

pronunciation, the Chinese meaning and how to use the word. But how can you know where the word

is thousands of English words? How to find it in the dictionary both quickly and correctly?

     First, all the English words are arranged (安排) in the letter order. In the dictionary you can first see

the words beginning with letter A, then B, C, D…. That means, if there are two words "desert" and "pull",

"desert" will be certainly before "pull". Then if there are two words both beginning with the same letter,

you may look at the second letter. Then the third, the fourth… For example, "pardon" is before"plough",

"judge" before "just", etc. 

     Do you understand how to look up in the dictionary?

     The dictionary will be your good friend. I hope you'll use it as often as possible in your English study.

1. This passage is about _____.[ ]

A. new words in writing

B. different dictionaries

C. the best way of reading

D. using an English-Chinese dictionary

2. In the dictionary you may not find _____.