Question

Select the sentence that uses an infinitive phrase as an object.

Answer 1

A.  Christa chose to write a literary critique of the novel Oliver Twist.

An infinitive phrase will include the word “to” in addition to a verb.  For instance, “to run,” “to sleep,” and “to laugh” are all infinitives.  If the word “to” is followed by a noun, “to” would be a preposition.  And, an object is the recipient of the action/verb.  With that in mind, in Option A we can see that “to write” is receiving the action “chose,” which makes “to write” a direct object.  

Answer 2

The only sentence here with an infinitive phrase is the first one, and the infinitive phrase there is 'to write'. You ask the question - What did Christa choose? in order to find the object of that sentence, and the answer is 'to write'.