A wire is suspended from the ceiling and stretched under the action of a weight F suspended from its other end. The force exerted by the ceiling on it is equal and opposite to the weight. 

a) Tensile stress at any cross section A of the wire is F/A. 

b Tensile stress at any cross section is zero. 

c) Tensile stress at any cross section A of the wire is 2F/A. 

d) Tension at any cross section A of the wire is F.

From the figure,

$\mathrm{Stress}=\frac{\mathrm{force}}{\mathrm{area}}=\frac{\mathrm{F}}{\mathrm{A}}$

The force applied to a wire when it is suspended from the ceiling and stretched by a weight (F) suspended from its other end is equal to and in the opposite direction of the force applied by the weight. 

The tension, however, is merely F and not 2F at any cross-section A of the wire. As a result, the tension per unit area, or tensile stress, is equal to F/A.

Hence the correct answer is only a & d are true.