It says that 배추 is correct when you hover over the word, but when you click it, it's incorrect
양배추 is the round cabbage we typically eat in America. 배추 is often called Napa cabbage, and is much more common in Korea. If a Korean asked me about cabbage, I would assume they are talking about 배추.
양 before food usually means "western". So to Koreans, 배추 means cabbage and 양배추 means western cabbage. But we call 배추 Napa cabbage .