Doubt from electromagnetic induction

Question 5

L is probably the diameter.

Should be B

Suppose the emf induced in part ACB is E, as shown.
Since the emf in the zero, emf(in ACB)+emf(∈BA)=0
,emf(in ACB)+emf(∈BA)=0
,or −E+vBL=0
But they have asked the emf induced the coil,
as the change in flux is zero.
the emf induced in the coil is zero