Computer Science for IGCSE & O level - Data Transmission (Section 1 - No. 2)

Which technique does a checksum employ to detect errors in data transmission?

Adding extra bits to the beginning of the data.

Calculating a numerical value and comparing it at the receiver.

Using a public key to encrypt the data.

Re-sending the data multiple times.

A checksum calculates a value from the data that is then compared at the receiving end.