The correct answer is B. stop bit.
A stop bit is a bit used in asynchronous serial communication to indicate the end of a transmitted byte. It is usually a 1 bit, and is always transmitted after the data bits and the parity bit (if present). The stop bit allows the receiver to determine when the byte has been received correctly.
A start bit is a bit used in asynchronous serial communication to indicate the beginning of a transmitted byte. It is usually a 0 bit, and is always transmitted before the data bits and the parity bit (if present). The start bit allows the receiver to synchronize its clock with the transmitter’s clock.
A parity bit is a bit used in some serial communication protocols to detect errors in transmission. The parity bit is calculated based on the value of the data bits, and is transmitted along with the data bits. The receiver calculates the parity bit for the received data bits, and compares it to the transmitted parity bit. If the two parity bits are not the same, an error is detected.
Data bits are the bits that carry the actual data being transmitted. The number of data bits in a byte varies depending on the communication protocol being used.
None of the above is not the correct answer.