Choose from the list below the changes in the head impacts that would reduce the acceleration during the impact.
1. A shorter impact time interval
2. A longer impact time interval
3. A shorter stopping distance
4. A longer stopping distance
5. A smaller initial speed
6. A larger initial speed
(a) 1,4,6
(b) 1,3,5
(c) 1,4,5
(d) 2,4,5
(e) 2,4,6