The development of the steam engine....of that is an option. You really should include the choices.
Martin Luther and the 99 thesis would accurately describe this since he initiated the protestant reformation which focused mainly on the bible and the ability for the lay people to read and understand it unlike Catholicism which was a hierarchy <span />
I think it’s d
a. is a person
b. is a group of people
c. is a person
d. is a unification