I do not know it should be B or C

Alex, Belinda and Cecilia are neighbours. One night, there was a severe storm that blew over Belinda's fences on both sides of the house adjoining Alex and Cecilia's. Alex agrees to fix Belinda's fences for a payment of $100.00. After hearing of their agreement, Cecilia agrees to pay a bonus of $50.00 to Alex if he fulfils his promise to Belinda. Assuming that the elements of offer, acceptance and intention exist, is the agreement between Cecelia and Alex enforceable?

1. A)No, because there is no consideration moving from Alex to Cecilia
2. B)No, because Alex is performing an existing obligation which is not good
3. consideration
4. C)Yes, because Alex's provision of an existing obligation to a different party can
5. amount to good consideration in the agreement with Cecilia
6. D)Yes, because offer, acceptance and intention are all satisfied and consideration is