The correct answer is D. Transceiver.
A transceiver is a device that both transmits and receives data. It is a combination of a transmitter and a receiver. The transmitter converts data into a signal that can be transmitted over a communication channel, and the receiver converts the signal back into data.
A transducer is a device that converts energy from one form to another. For example, a microphone converts sound waves into electrical signals, and a loudspeaker converts electrical signals into sound waves.
A trapdoor is a hidden entry point into a computer system. It is often used by hackers to gain unauthorized access to a system.
A translator is a person or device that converts text or speech from one language to another.
None of the above options is a device that both transmits and receives data.