Answer:
a. mass
Step-by-step explanation:
Lighting a fireworks the potential energy is converted to all forms of energy like light, heat and sound energy . According to the law of conservation of energy the energy packed inside the fireworks before it ignites must be equal to the the total remaining after it explodes in addition to the energy released as light , heat and sound. In other words no mass is loss in the conversion of energy(energy can neither be created nor destroyed but can be change from one form to another) .
The energy was only converted to other forms of energy like light, heat and sound but their is no overall loss in the mass.