Which expression is equivalent to 21 + 49?
A 7(3 + 49)
B 7(3 + 7)
C 7(14 + 42)
D 7(14 + 49)
A 7(3 + 49)
B 7(3 + 7)
C 7(14 + 42)
D 7(14 + 49)