Which words make up the prepositional phrase in this sentence?

haakon built a tree house for his younger brother and sister.

a.
brother and sister

b.
haakon built

c.
a tree house

d.
for his younger brother and sister

While in prison, malcolm's introduction to the elijah muhammad's teachings forces him to reflect on his own past experiences. why do those experiences persuade him to join the nation of islam? what, in malcolm's experiences, draws him to an activism more militant than the nonviolent activism of martin luther king jr?