The area of a square depends on the length of its sides. This can be written in function notation as a (s). What is the best interpretation of a(2) = 4

A. The area of a square is always two times the side length.
B. A square with sides 4 units long has an area of 2 square units.
C. The area of a square is always one-half of the side length.
D. A square with sides 2 units long has an area of 4 square units.