Antenatal testing

Which of the following constitutes a "reactive" non-stress test (NST)?

1: At least 2 fetal heart rate decelerations over 20 minutes
2: At least 2 fetal heart rate decelerations over 40 minutes
3: Less than 2 fetal heart rate accelerations over 40 minutes
4: At least 2 fetal heart rate accelerations over 20 minutes