In blast injuries we split injuries into four parts. Primary blast injuries are dangerous because the expanding pressure and gas can cause the hollow organs of the body to rupture. The is massive rupturing can kill near instantaneously.
Secondary injuries are were things are actually life threatening by flinging stuff. Shrapnel, burns, debris can hit a patient.
Tertiary Injuries are noted as the next thing up, which is a patient can be flung away from the explosion, with collision into another object and the possibility of secondary impalation or blunt force trauma is possible. This is heavily reliant on the distance of impact.
So your answer is A.