Answer
Choice B.
Work Step by Step
The magnitude of the induced electric field is given by Faraday’s Law.
$$\epsilon=\frac{d\Phi_B}{dt}= A\frac{dB}{dt}$$
We see that the greater the area A, the greater the flux, and the faster the rate of change of the flux in a given time.
The largest area has the greatest induced emf. This is the periphery of the dashed line.
