Answer:
D -2
Explanation:
any triangle inscribed into a half-circle is a right-angled triangle.
that means the triangle angle at B is 90°.
so, BC and AB are always perpendicular to each other (90° crossing angle).
remember, when the original slope is y/x, then the perpendicular slope is -x/y.
so, in our case the original slope of BC is 1/2.
therefore, the perpendicular slope (the slope of AB) is then
-2/1 = -2