call
[误] I'll call at Mr Brown.
[正] I'll call on Mr Brown.
[误] I'll call on Mr Brown's home.
[正] I'll call at Mr Brown's home.
[析]作"拜访"讲时， at后面接访问地点，而 on后面接访问的人。
call on drop in visit
call on比较正式的为公务的访问，如： We were called on by the old students. 而 drop in则是比较随便的走走，顺便拜访，如： If you're free, drop in. 而 visit则是更正式的外交访问或友好往来，如： My school's headmaster will visit America next week.?
can
[误] A blind man can not judge colours.
[正] A blind man cannot judge colours.
[误] I cann't call for you at ten.
[正] I can't call for you at ten.
[析] can的否定形式应为 cannot或 can't.
[误] It's only six o'clock. That mustn't be the postman.
[正] It's only six o'clock. That can't be the postman.
[析] must用来表示一种肯定的推断，如： She must have some problems. She keeps crying. 但在否定句中则要用 can't，要表示对过去的推测则要用" must+ have+过去分词"的表达法，如： The lights have gone out.A fuse must have blown.而对过去的否定推测则多用" can't?+ have+过去分词"，如： I don't think he can have heard you. Call again.
[误] We could not help to laugh at once.
[正] We could not help laughing at once.
[正] We could not help but laugh at once.
[析]" couldn't help+动名词"表示禁不住做了某事。但 could not help but与 could not but后面要加不带 to的不定式，意思都是不得不去做某事.如： You could not (help) but respect him.
can be able to
can与 be able to都可以用来表示能力，但 can只有现在时与过去时， be able to则可用任何时态，如： He will be able to teach the child. 但要表示经过努力而达到的一次性动作则只能用 be able to，如： He finally was able to jump over 2? 10 meters. 或： The plane was able to fly over the mountain. 但要注意的是这两个词都没有进行时态，而 be able to后面不接不定式的被动态。
can could
can与 could都可以用在现在时的口语中，只是用 could更为礼貌，语气更委婉。如： Could you tell us a story
care
[误] I don't care coffee.
[正] I don't care for coffee.
[误] Take care for your steps.
[正] Take care of your steps.
[析] care for是"对某物感兴趣"，而 care of是"关心，要当心某事"，如： She didn't care for him. Take care of what you are doing.
[误] I don't care where we will go if it doesn't rain.
[正] I don't care where we go if it doesn't rain.
[析]在 it doesn't matter, I don't care, I don't mind,及 in case引出的状语从句后面要用现在时表示将来。如： I've got a football in case we have time for a game.
change
[误] I want to change my camera with that one.
[正] I want to change my camera for that one.
[析] change for为"以某物为交换物"。而 change with则是"随……而变"，如： The wood's colour changed with the season.
cheap
[误] A teacher's salary is generally very cheap.
[正] A teacher's salary is generally very low.
[析]工资的高低要用 low， cheap是指价格便宜，如果要讲物美价廉则要用 not expensive,如： This car is not expensive.
choose
[误] We each had to have a choose of A or B.
[正] We each had to have a choice of A or B.
[析] choice是名词，而 choose是动词。
class
[误] The class is watching TV.
[正] The class are watching TV.
[析] class作主语时，如果作为整体讲则应用单数形式的谓语动词，如： The class was more than forty in number. 如考虑到具体的每个成员时则应用复数形式的谓语动词，如： The class are, in general, very bright.
clean
[误] Sorry, I didn't bought it here. I cleanly forgot.
[正] Sorry, I didn't bought it here. I clean forgot.
[析] clean可以作为副词讲，其意为"完全"，而 cleanly则意为"正确地"、"干净利落地"，如： The knife doesn't cut cleanly. 而 clean作为形容词讲时意为"清洁的"、"干净的"，如： Her face is not clean now.
