Here is the original item:
Mackenzie had to leave the room,
(A) for her
father was noisily crunching raw radishes,
(B) which
produced so annoying a sound
(C) that
studying was impossible.
You wanted to do this:
McKenzie had to leave the room, for her father
was noisily crunching raw radishes. Which produced
so annoying a sound that studying was impossible.
Adding a period after radishes makes a fragment. Which produced so annoying a sound ... begins a subordinate clause. Remember that a subordinate clause cannot stand alone as a complete sentence.
You might want to review the rules.