To be honest im in middle school and this is quite tricky.but ill try my best.
Answer:
Money
Step-by-step explanation:
In this case, Lydia does not have enough money to buy a birthday present for her sister, pay her car insurance and buy herself a prom dress. Money is always a scarce resource, and in this case she is $1 short. She could get the money from her bank account but that would lower her savings for college. Money for college is also scarce.