Explanation:

- In computer systems, INTR and WR signals are commonly used in input/output (I/O) operations.

INTR Signal:
- The INTR (interrupt) signal is an input signal pin that is used by devices to request attention from the CPU.
- When a device wants to interrupt the normal execution of the CPU, it asserts the INTR signal by sending a logic high (1) to the input pin.
- The CPU then responds to the interrupt by suspending its current task and servicing the requesting device.

WR Signal:
- The WR (write) signal is an output signal pin that is used by the CPU to indicate to the I/O device that it wants to write data to it.
- When the CPU wants to write data to an I/O device, it asserts the WR signal by sending a logic high (1) to the output pin.
- The I/O device then reads the data from the CPU's data bus and processes it accordingly.

Combination of INTR and WR Signals:
- In I/O operations, the INTR and WR signals work together.
- When an I/O device wants to request attention from the CPU, it asserts the INTR signal.
- The CPU, upon receiving the INTR signal, suspends its current task and responds to the interrupt.
- As part of the interrupt handling process, the CPU may need to write data to the I/O device.
- In this case, the CPU asserts the WR signal to indicate that it wants to write data.
- The I/O device then reads the data from the CPU's data bus and processes it accordingly.

Conclusion:
- Therefore, the INTR signal is an input signal pin used by devices to request attention from the CPU, while the WR signal is an output signal pin used by the CPU to indicate that it wants to write data to an I/O device.
- Since one signal is an input signal and the other is an output signal, the correct answer is option 'C' - one is input and the other is output.