Answer:
a - continuity
Step-by-step explanation:
continuity is the unbroken and consistent process or existence or something over a period of time
in this case, as you age your body begins to break down. since aging would be considered continuity the result (in this case) would be their reaction speed decreasing
so since the overall effect or slower reaction time is a result of a continuing process this is an example of continuity
hope this helps :)