Lets examine each option :

option a) F1(x) = –F(x) ; it will result the graph mirror image with respect to X -axis . So when we take the mirror image of F(x) with respect to X axis . we didnt get F1(x) . so option a is wrong

option b) F1(x) = F(–x) ; it will copy the graph which is left to y axis to right to y axis and vice versa . As f(x) is symmetric to y axis . so you will not see any change in the graph of F(–x) . so this option is also not correct .

option c) F1(x) = –F(–x) ; as we know from option b that F(-x) is same as F(x) . so -F(-x) will be same as option a . so this one is also not correct .

So ans is option D (None) :)