(1) if all those who run their dogs also walk their dogs, then number of dog owners who run their dogs will either be equal to those who walk their dogs OR it will be less than those who walk their dogs (latter will be the case where there are some owners who only walk their dogs and not run).

In any case, number of those who run their dogs can never be greater than those who walk their dogs. So this statement is sufficient to answer the question with a NO.

(2) 75 walk their dogs, but nothing given about those who run their dogs.
Not sufficient.

Hence A answer.

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