Which sentence is parallel?

Identify the sentence that is parallel.

a)

He sings in the choir, is a volunteer at a food bank, and is always doing good deeds.

b)

He sings in the choir, volunteers at a food bank, and does many good deeds.

c)

He sings in the choir, volunteers at a food bank, and is always doing good deeds.

d)

He is singing in the choir, volunteers at a food bank, and does many good deeds.