ACTIVATE: DETONATE::

The relation is one of degree or intensification of action. To activate is to make something start functioning, while to detonate is a stronger, more forceful act causing an explosive result. Among the choices, to deaden is to reduce sensation or force, while to defuse is a stronger act that neutralizes danger completely. The pair best matches the progression in intensity and effect. After checking all options, $(A)$ is the best analogy.