A prepositional phrase starts with a preposition; it also includes the object of the preposition and any modifiers of the object.
C starts with the <em>preposition</em> to and includes the <em>object </em>of the preposition structure and two <em>modifiers</em> of the object your, sentence.
The prepositional phrase in this sentence is c. "to your sentence structure", because it is postmodifying an infinitive phrase (to bring complexity), which has the same value, in this case, as a noun phrase. Besides it is composed by a preposition (to) and a noun phrase (your sentence structure).
Option a. is a verb phrase as well as option b. In the same way, letter d. is not a prepositional phrase as it is an adjective phrase used in the comparative form.
Because as it said in the previous question it said that "a thick dust covered survivors and first responders at ground Zero" If you look at the other questions they do not support the answer u have in the previous question I hope this helps and i am sorry if i a wrong but this is what I think
