Here main keyword is “without wasting any money” that means he/she don’t want any credit for surplus. He wanted to buy that number of tickets for which he/she could use exact number of coins. He/she have 14$ total.
So lets check answer options:
A) For 11$ ticket he/she can spend 12$ as (5$+5$+2$) so 1$ remains as credit.
B) He/she can buy a 4$ (2+2) ticket without any surplus but for a 7$, he have spent 10$ (5$+5$) so 3$ will be surplus.
C) For three 2$ tickets (6$), he can either use 7$ (5$+2$) or use two 5$ coins or may be 9$ (2$+2$+5$). All of above could lead to some extra $.
D) This is the best combination. Three 3$ tickets=9$. If he/she use one 5$ coin, two 2$ coins (total 9$) then all of the amount would be spent and no extra extra credits.
E) Two 9$ tickets=18$. That’s not possible to buy as he/she have a total of 14$.