Gate overflow

Question

If F(x,y,z) =((F1(x,y,z) + F2(x,y,z)) + (F3(x,y,z))')' where F1(x,y,z) = sigma(2,4,6,7), F2(x,y,z) = sigma(5,7) and F(x,y,z) = sigma(2,5,7) then what is the value of F3(x,y,z) ?

A) sigma (2)

B) sigma (2,4,5)

C) sigma (2,5,7)

D) sigma (2,4,6,7)

Answer 1

I think something is wrong in this question