A simple pendulum is suspended inside a truck moving uniformly with a small acceleration of $‘2a’.$ Its mean position as an angle in radians with respect to the vertical is

Question

$\begin{array}{1 1}(a)\;0\\(b)\;\frac{2a}{g} \\( c)\; 6.28 \\(d)\; None\;of\;the\;above \end{array}$