Interesting point on filters and sub selects, but I thought the question was a bit misleading in terms of the possible answers provided:

- From a syntax point of view, I agree 'B' would the correct answer

- From a results/holistic view, 'C' would be the answer as the query (using the attached example) yields incorrect results as there is no filter on the join and only Customer 1 is on pricing plan 'X', but results say both customers are on pricing plan 'X'?