Which is a correctly written sentence, not a run-on?

a. Tomatoes in our garden are ripening; they will be delicious in a salad.

b. Dog-sitting is fun and challenging it takes patience and organization.

c. Jacaranda trees have fernlike leaves, they bloom purple flowers in spring.

d. A bird laid eggs in a nest on the patio they should be hatching soon.

All these sentences need a semicolon (; )

a. Tomatoes in our garden are ripening; they will be delicious in a salad.

b. Dog-sitting is fun and challenging; it takes patience and organization.

c. Jacaranda trees have fernlike leaves; they bloom purple flowers in spring.

d. A bird laid eggs in a nest on the patio; they should be hatching soon.

The answer is A. because it already has a semicolon