Which sentence contains correct parallel structure?
a.
He wanted three things out of the class: learning a new skill, making new friends, and to develop a different mindset.
b.
He wanted three things out of the class: to learn a new skill, to make new friends, and to develop a different mindset.
c.
He wanted three things out of the class: to learn a new skill, making new friends, and developing a different mindset.
d.
He wanted three things out of the class: learning a new skill, to make new friends, and to develop a different mindset.