A pulse traveled the length of a stretched spring.

The pulse transferred

(1) energy, only

(2) mass, only

(3) both energy and mass

(4) neither energy nor mass

So we want to know to what is the pulse transformed that traveled the length of a stretched spring. So a pulse is a part of a mechanical wave, and mechanical waves are energy transfer trough some medium, in this case a stretched spring. So the correct answer is (1) energy. The pulse cant be transferred into mass.