**A) 1.33 N/mm2**

B) 2.67 N/mm2

C) 4 N/mm2

D) 5.33 N/mm2

Reference:

As per IS 456:2000, the shear stress formula is:**τ = VQ/Ib**

Where,

τ – Shear stress

V – Shear force

Q – First moment of area above or below the neutral axis

I – Moment of inertia

b – Width of beam

For a rectangular section, **I = bd3/12**

Q = A x centroidal distance from neutral axis

Here,

b = 300 mm

d = 500 mm

V = 20 kN

Depth at which shear stress is required = 150 mm

∴ I = (300 x 5003)/12 = 7.5 x 108 mm4

Q = (150 x 300) = 45 x 104 mm3

**τ = (20 x 103 x 45 x 104) / (300 x 7.5 x 108)**

**∴ τ = 1.33 N/mm2**

**Therefore, option A is the correct answer**.