02br 02br 00In your example, knowledge is a non-count noun. 02br 02br 00The word "effort" however can be both count or non-count depending on usage. e.
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01cite10Anonymous12cite10Thank you, it was 11u10a great knowledge enhancer12u10.12blockquote10I'm not sure if this was from the same 'Anonymous' but in the underlined text, the noun is actually enhancer, and not knowledge. Using 'a' here is acceptable, if that was what you were trying to say.