“All Socs aren't like that,” she said. “You have to believe me Ponyboy. Not all of us are like that”

Pony Boy cannot seem to understand why anyone that was a Soc would have any problems.  He thinks they have all they need with fine homes and money...

Greasers, on the other hand, are much poorer than the Socs and do not have the financial means that Socs have.  They also snub the Greasers.

Explanation:

Why would the Socs have problems if they have money?  

This is how Pony Boy thinks...

he agrees with the monk's positions.

the correct answer is 4) infinitive phrase with a direct object

the explanation is that the infinitive phrase, "to with the younger children", functions as the object. it means the thing that the subject does.

1) no infinitive is incorrect because there is an infinitive verb in the sentence.

2) an infinitive only is incorrect because it is not in isollation. it is part of an infinitive phrase.

3) infinitive phrase with a subject is incorrect because in this example the infinitive phrase does not function as the subject doing the action of the sentence.