A coil in the shape of an equilateral triangle of side $0.02 m$ is suspended from vertex such that it is hanging in a vertical plane between the pole-pieces of a permanent magnet producing a horizontal magnetic field of $5\times {10}^{-2}T$. Current in loop is 0.1 A. Then

Area of triangular loop $=\frac{1}{2}\times l\times l\sin 60° =\sqrt{\text{3}}\times {\text{10}}^{-\text{4}}{\text{\hspace{0.17em}m}}^{\text{2}}$
So, magnetic moment,  $M=iA=0.1\times \sqrt{3}\times {10}^{-4} =\sqrt{\text{3}}\times {\text{10}}^{-\text{5}}{\text{A-m}}^{\text{2}}$
Hence choice (a) is correct and choice (b) is wrong.
Couple acting on loop $\tau =MB\sin \theta =(\sqrt{3}\times {10}^{-5})(5\times {10}^{-2})\times \sin 90°$ 

$=5\sqrt{3}\times {10}^{-7}\text{\hspace{0.17em}N-m}$
Hence, choice (c) is correct and choice (d) is wrong.
$\therefore$ (a) and (c) are correct.