noun
1
BAD : I'm taking an intermediate course of English.
GOOD : I'm taking an intermediate course in English.
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a course in/on sth (NOT of ): 'I've been attending an evening course in business studies.' 'I'm interested in doing a correspondence course in English and Maths.' 'There is also a two-day course on new technology for teachers.'
2
BAD : The boys and girls in my English course come from all over the world.
GOOD : The boys and girls on my English course come from all over the world.
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In British English you say that someone is on a course : 'Some of the people on the course came to a few classes and then dropped out.'
Note that in a course is used in American English.
3
DUBIOUS : We'll probably go to the cinema or to a discotheque. Of course, since Fiona is my guest, I'll let her decide.
GOOD : We'll probably go to the cinema or to a discotheque. Naturally, since Fiona is my guest, I'll let her decide.
DUBIOUS : The construction of a new motorway is totally unnecessary and of course the local residents are completely against the idea.
GOOD : The construction of a new motorway is totally unnecessary and, as one would expect, the local residents are completely against the idea.
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Of course is generally over-used. Common words and phrases that may be used as alternatives include: naturally, obviously, clearly, certainly, evidently, predictably, as you/one would expect, as is to be expected, as you know, it is clear/obvious that.