The answer is: A
Explanation
The correct option is A. B and C must file separate suits, as A has entered into separate agreements with B and C. The principle states that all persons may be joined in one suit as plaintiffs, provided that the right to relief alleged to exist in each plaintiff arises out of the same act or transaction and the case is of such a character that, if such persons filed separate suits, common questions of law and facts would arise. In this case, A's failure to supply B and C with fruits is not the same act or transaction, but two different breaches of contract. B and C have different causes of action against A, and they cannot claim the same relief.
Therefore, they cannot file a suit together. The other options are incorrect because they do not satisfy the condition of the principle.