Answer:
Option A, irresponsible
Step-by-step explanation:
William was not intentionally "irresponsible" but due to his careless behaviour a man was killed by his car. He must have focused on the road rather than on changing the radio station. And in case if wanted to do so he must have visualized the traffic condition and then must have stopped or slow down his car before doing so. Since he continued with the same speed while changing the radio station, his car struck a man and led to his death. Thus, it is the fault of William somewhere.