To investigate or research into it
I think it is c because a rhetorical question is <span>a question asked in order to create a dramatic effect or to make a point rather than to get an answer.</span>
The purpose of King's letter is to cause the Church to fight racial injustice.
As you already know, King was a proponent of equal human rights, for both black, and white people. He wanted the Church to be aware of inequalities in the world and fight racism so as to erase those inequalities.
Answer:
COMPOUND:he wrote the diary in short hand; the diary was decode