when is the absolute velocity of end B of the coupler equal to the absolute velocity of the end A of the coupler?

Question

 

In the figure given above, when is the absolute velocity of end B of the coupler equal to the absolute velocity of the end A of the coupler?

(a) $\Theta _{2}=90^{o}$

(b) $\Theta _{2}=45^{o}$

(c) $\Theta _{2}=0^{o}$

(d) Never