Two plane mirrors at an angle such that a ray incident on a mirror undergoes a total deviation of $\text{240°}$ after two reflections.

$\text{d}=360-2\theta$

$\Rightarrow 240=360-2\theta$

$\Rightarrow \theta =60°$

(B) $\frac{360}{\theta }=6$ This is even. As the object is placed symmetrically

between the mirrors$\text{N}=\frac{360}{\theta }-1=5$

(C)If the object is placed un symmetrically$\text{N}=\frac{360}{\theta }=\frac{360}{60}=6$

(D) When a ray incidents on ${\text{M}}_{\text{1}}\text{at}60°$  it falls on${\text{M}}_{\text{2}}$  normally as

shown in figure.