A semiconducting device is connected as shown in the figure

A current is found to pass through the circuit. On reversing the polarity of the battery. The current in the circuit drops to almost zero. What is this device?

a p-n junction diode

If the polarity of the battery is reversed, the current drops to almost zero. The device may be a p-n junction diode. 

For a diode in reverse biasing mode resistance become infinite and hence current becomes almost zero.