Final answer:
Marcus, aspiring to apply to medical school, would likely be the most willing to donate blood to Plattsville blood bank to gain experience and demonstrate his social responsibility.
Step-by-step explanation:
The most likely candidate to contribute to the Plattsville blood bank would be: a. Marcus, who wants to apply to medical school when he is older. Marcus, aspiring to attend medical school, likely has a keen interest in healthcare and understands the importance of blood donation. His future career goals may motivate him to contribute to the community's well-being by donating blood. Additionally, individuals aspiring to join the medical field often possess a strong sense of altruism and social responsibility, making Marcus a probable candidate to step forward and donate. It's worth noting that while various factors influence people's willingness to donate blood, Marcus's career aspirations align closely with the values associated with blood donation, making him the most likely candidate among the options provided.