AMC8 2024 Problem 7

A 3 \times 7 rectangle is covered without overlap by three shapes of tiles: 2 \times 2, 1 \times 4, and 1 \times 1, shown below. What is the minimum possible number of 1 \times 1 tiles used?

Answer Choices
A. 1
B. 2
C. 3
D. 4
E. 5