It's been more than ten days since I posted this question here and I'm still looking forward to your kind help. A question like this may sound stupid but it's a real difficulty for an ESL like me. Just now I was reading DISCOVER CANADA and came across this sentence:
Immigrants between the ages of 18 and 54 must have adequate knowledge of English or French in order to become Canadian citizens.
I've benefited a great deal from this great forum and I'm grateful for all your help. But I just don't know when to use a/an and when not to in the case of 'knowledge'. Could anyone give me some explanation please? A thousand thanks in advance.
Student or Learner