Which expression is equal to 839?

A. (8 x 101) + (3 x 100) + 9
B. (8 x 102) + (3 x 101) + (9 x 100)
C. (8 x 103) + (3 x 102) + (9 x 101)
D. (8 x 104) + (3 x 103) + (9 x 102)