I've come across a question while writing an exam
Roger really excelled ___ sports
My first thought was 'in', later I remembered using 'at' also. I've searched for this in a few forums, there they say both 'excel in' and 'excel at' are correct expressions and could not really make out any differences.
Now my problem is that I'm an ESL and the above question doesn't give options like 'both a and c correct'. I'm not sure what option to pick for these kind of questions.
So, what is the correct option for above question?. Answers from experts are much appreciated. If both are correct what is the intention of question paper setter?