In an electric circuit, there is a cell which has two terminals, positive and negative. The current leaves from the positive terminal and enters from the negative terminal to complete the electric circuit. A positive terminal on a cell is shown by a (+) sign or the side where you will observe a small cap like outing cover. So, in the figure, you can observe that only in Fig. B the current leaves from positive terminal and enter back in the negative terminal. But in another figure this is not shown hence B is the correct answer.