There should be options for this question. I managed to find them elsewhere. They are:
Body composition; she is on track to significantly improve in this area based on this program
Cardiovascular endurance; she will never reach this goal unless she adds weightlifting to her routine
Flexibility; she is on track to significantly improve this area of fitness by sticking with this program
Muscular strength; she will only improve in this area if she adds cardio to her workout schedule
The correct answer is the third option. By doing stretching yoga three times each week Natalia is targeting her Flexibility. Practicing yoga helps to make your muscles more flexible and agile. Her potential is that she is on track to significantly improve this area of fitness, because of the amount of times she is doing the yoga and by sticking with this program.