Question

read the sentences.
mark zuckerberg created a messaging network as a preteen. he co - founded facebook while still in college.
now combine the sentences by completing the relative clause.
mark zuckerberg, who
, co - founded facebook while still in college.

Explanation:

To combine the sentences using a relative clause, we use "who" to refer to Mark Zuckerberg. The correct combination is "Mark Zuckerberg, who created a messaging network as a preteen, co - founded Facebook while still in college." So the word to fill in the blank is "created a messaging network as a preteen, co - ".

Answer:

created a messaging network as a preteen, co -