Defining "bisect" is a good first step in figuring this one out; when we say an angle or a line is being "bisected," we mean that it's being split in half, into two equal angles/line segments. Here, the line segment FI seems to be dividing the line segment EG in half, as evidenced by the congruent line segments EF and FG. Notice too that the angle the line forms, ∠EFI, is right. What keyword in those four options has something to do with right angles?
