Ruby is buying chocolates for her friends. The candy store charges $13.80 for a box of chocolates, and each additional piece of chocolate costs $0.23. Ruby has $21 to spend. She buys x additional pieces along with a box of chocolates. Which inequality correctly represents the given situation?

A.0.23x + 21 ≤ 13.8
B.13.8 + 21 ≤ 0.23x
C.13.8 + 0.23x ≤ 21
D.13.8 + 0.23x ≥ 21