Horace mann is known primarily for his efforts in which reform movement?
a.
education reform
b.
prison reform
c.
the abolition movement
d.
the temperance movement

Horace Mann was known for his work in education reform. There's even a famous private school named after him for exactly this reason. Your best answer is A.

Primary sources are usually  more accurate and are written by someone who experienced it or witnessed it. secondary sources are those who heard of it after the fact that can lose details and or twist the event in a light that benefits them.