The answer is C. This answer is best solved
Logically - there's no need to actually solve it, but only to examine if there is enough information to do so.
There are 4 potential groups: just coffee, just tea, both, and neither. We need to find one (neither), so we need the 3 others in order to find it.
Starting off, we have none of the groups (knowing how many took coffee or tea doesn't tell us the size of any of the 4 groups). 1) and 2) on their own don't bridge this gap - neither is enough to know the size of 3 of the groups.
combined, however, we do have enough info: 1) tells us the size of a) just coffee, from which we can find b) both. from 2) we can find c) just tea - that's enough to find d) neither!!! answer C.
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65% (02:01) correct 
