Final answer:
The most important runner when there are multiple people on base is the closest runner to home plate.
Step-by-step explanation:
When there are multiple people on base, the most important runner is typically the closest runner to home plate, which is option b) in the question. This is because the closest runner has the shortest distance to travel to reach home plate and has the best chance of scoring a run. The fastest runner may not necessarily be the closest to home plate, so their speed may not be as advantageous in this situation.