Translation:Because it is interesting, I study Japanese.
"I study Japanese because it is interesting" was accepted, but I realize now that it's not a proper translation here.
What I learned in my Japanese class is that putting から at the end would be like putting because in the middle of English sentences. How I would have translated it is this:
日本語をべんきょうします。おもしろいですから。 The use of periods instead of a comma here is because verbs tend to go at the end of sentences, but this means the same as "I study Japanese because it is interesting."