A
point source is to be used with a concave mirror to produce a beam of
parallel light. The source should be placed midway between the center
of curvature and the mirror. To solve this question you have to draw
a ray diagram. Apply the mirror equation to determine the image
distance and finally make sure that the first two steps are
consistent with each other.
<span>I
hope this helps, Regards.</span>
For this case, the switch is located at point B of the diagram.
Remember that point D is the universal symbol for resistance.
In A what you have is a source of power and in C what you have is a cable.
Therefore, the answer for this case is B.