Question

select the two prepositional phrases. facebook co - founder mark zuckerberg began his programming career at age twelve, when he created a messaging program he called \zucknet,\ which was used in his fathers dental practice.

Explanation:

A prepositional phrase starts with a preposition and ends with a noun or pronoun. In the given text, "at age twelve" starts with the preposition "at" and "in his father's dental practice" starts with the preposition "in".

Answer:

at age twelve, in his father's dental practice