Question

One achievement of St. Thomas Aquinas was _____. becoming a bishop at a young age serving as a professor at the imperial court of Milan translating the Scriptures from Latin into medieval French reconciling Aristotle's logic with principles of the Roman Catholic faith

Answer 1

reconciling Aristotle's logic with principles of the Roman Catholic faith

Answer 2

According to the biography of Thomas Aquinas, he wanted to combine statements from the catholic church and Aristotel's ideoligy, so I would say that instead of gap there shoul be : Thomas Aquinas was reconciling aristotle's logic with principles of the roman catholic faith.
I'm sure that helps even though you did not give the options.