(18) In martial arts, they become better at self-discipline the longer people train. (19) They learn that self-discipline and determination are needed to advance in martial arts. (20) By constantly pushing themselves to improve, people learn to conquer self-doubt. (21) This determination can even lead to better grades and behavior at school. (22) One study revealed that students' behavior in school improved after they attended just 10 weeks of martial-arts training thanks to its emphasis on self-discipline.
What is the BEST way to revise sentence 18 to make the meaning more clear?
Question 4 options:
The people that become better at self-discipline, they train in martial arts longer.
The people that train in martial arts become better at self-discipline longer.
The longer people train, they become better at self-discipline in martial arts.
The longer people train in martial arts, the better they become at self-discipline.