For those who want to learn more about modal verbs, here are two old entries which might help you have a better understanding of these confusing words:
http://www.tiec.tp.edu.tw/lifetype/post/1130/25216
http://www.tiec.tp.edu.tw/lifetype/post/1130/25254
The best way to master them is to make sentences with them.
In today’s class, some students don’t understand a sentence in the Cloze on the review test. Here is how I analyze it. Here is the test items:
… For example, potato chips were invented because the chef George Crum got angry when a guest __27__ complained Crum’s French fries were too thick refused to have them. Crum then remade the fries very thin adn crispy so that teh guest would have trouble eating them with a fork.
___27. (A) which (B) who (C) X (D) being
The answer is ________.
This website offers very concise explanation of the passive voice.
http://www.npc.edu.hk/staff/~ngtungying/english_grammar/lessons/lesson35.htm
Please click 主詞與動詞的一致.doc
You might like to get some idea from this website:
http://blog.sina.com.tw/suchin/article.php?pbgid=18254&entryid=3195