If a and b are the end points of a line, then which one of the following is true?

In the Cohen-Sutherland line clipping algorithm, each endpoint of a line segment is assigned a 4-bit region outcode (Top/Above, Bottom/Below, Right, Left) relative to the clipping window. If both endpoints lie in the same outside half-plane—that is, both are to the left, both are to the right, both are above, or both are below the window—the bitwise logical AND of their region codes is non-zero, and the line segment is guaranteed to lie completely outside the window, making it trivially invisible (trivially rejected).