A circuit element is placed in a closed box. At time t=0  , a constant current generator supplying a current of 1 amp is connected across the box. Potential difference across the box varies according to graph shown in figure. The element in the box is:

On supplying a constant current of 10 amp in the circuit element, the potential difference across it is increasing, therefore, it should be a capacitor because on supplying the current, charge on the capacitor will increase. Hence, the potential difference across it will also increase.