To solve this question, the user needs to have knowledge of IRQ (Interrupt Request) and the devices that commonly use specific IRQ numbers.

IRQ is a mechanism used by devices to request the attention of the CPU. Each device in a computer system is assigned a unique IRQ number to prevent conflicts when multiple devices try to use the CPU simultaneously.

Now, let's go through each option and explain why it is right or wrong:

A. COM1: This option is incorrect. COM1 typically uses IRQ 4, not IRQ 3. Therefore, there would be no conflict between a network adapter on IRQ 3 and COM1.

B. COM2: This option is incorrect. COM2 typically uses IRQ 3, which means there could be a conflict between a network adapter on IRQ 3 and COM2. Both devices may try to use the same IRQ, leading to conflicts.

C. Keyboard: This option is incorrect. The keyboard typically uses IRQ 1 or IRQ 12, not IRQ 3. Therefore, there would be no conflict between a network adapter on IRQ 3 and the keyboard.

D. Hard Drive Controller: This option is incorrect. The hard drive controller typically uses IRQ 14 or IRQ 15, not IRQ 3. Therefore, there would be no conflict between a network adapter on IRQ 3 and the hard drive controller.

E. Display Card: This option is incorrect. The display card typically uses IRQ 9 or IRQ 11, not IRQ 3. Therefore, there would be no conflict between a network adapter on IRQ 3 and the display card.

Based on the explanations above, the correct answer is:

The Answer is: B. COM2