The sentence in which the underlined infinitive phrase functions as a subject is the last one - to quickly move large groups of people is the purpose of public transportation.
<em>To quickly move </em>is the infinitive phrase, and it is a subject.
D. He thinks the wind will change and bring them to shore.
Bob Ewell was killed by Boo Radley, who stuck a kitchen knife into his chest on the night of Halloween. Bob wanted to get revenge on Atticus for trying to kill the children who were walking back from a Halloween school party.
