If A + B = C, D - C = A and E - B = C, then what does D + F stand for?

Correct option is B

Assume that each character represents the number equivalent to the position in the alphabet i.e. A = 1, B = 2, C = 3, D
= 4 and so on. Now let's check our assumption.

A + B = C i.e. 1 + 2 = 3
D - C = A i.e. 4 - 3 = 1
E - B = C i.e. 5 - 2 = 3
Thus, our assumption was Correct. Hence, D + F = J i.e. 4 +
6 = 10