Answer:
The correct option is A.
Explanation:
If a figure dilated by a scale factor of k with a center of dilation at the origin, then

It is given that rectangle ABCD is dilated by a scale factor of 1/2 with a center of dilation at the origin, so

The coordinates of B are (-4,6). So, the coordinates of B' are


The coordinates of B' are (-2,3), therefore option A is correct.