To determine which diode is forward biased, we need to check the voltage across the diode.$\\$A diode is forward biased when the anode is at a higher potential than the cathode.$\\$Let's analyze each option:$\\$Option 1:$\\$• Anode voltage: $-4 \,$V$\\$• Cathode voltage: $-3 \,$V$\\$• The anode is at a lower potential than the cathode, so the diode is reverse biased.$\\$Option 2:$\\$• Anode voltage: $-2 \,$V$\\$• Cathode voltage: $+2 \,$V$\\$• The anode is at a lower potential than the cathode, so the diode is reverse biased.$\\$Option 3:$\\$• Anode voltage: $3 \,$V$\\$• Cathode voltage: $5 \,$V$\\$• The anode is at a lower potential than the cathode, so the diode is reverse biased.$\\$Option 4:$\\$• Anode voltage: $0 \,$V$\\$• Cathode voltage: $-2 \,$V$\\$• The anode is at a higher potential than the cathode, so the diode is forward biased.$\\$Therefore, the correct option is Option 4.