Language-learners who say they never or hardly ever use dictionaries often speak English well but usually write poorly, because they make many mistakes. The students who use dictionaries most do not learn especially well either. The ones who look up every new word do not read fast. So they do not have time to read much. Those who use small two-language dictionaries have the worst problems. Their dictionaries often give only one or two words as translations   of English. But one English word often has many translations in a foreign language and one foreign word has many translations in English. The most successful students are those who use large college edition dictionaries with about 100,000 words but do not use them too often. When they are reading, these students first try to get the general idea and understand new words from the context. Then they reread and use the dictionary to look up only key words that they still do not understand. They use dictionaries more for writing. If they are not sure how to spell a word, or divide it into syllables  , they always use a dictionary. Also, if they think a noun might have an unusual plural form, they check these in a dictionary. This passage mainly tells us  _  .
that students shouldn't use small two-language dictionaries what were the defects   of small two-language dictionaries why students should use large college edition dictionaries what dictionary students should choose and how to use it