You Propose a Code in Which Each Two-Digit Binary Message

Multiple Choice

You propose a code in which each two-digit binary message word a₁ a₂ has appended a parity-check digit c₁ = a₁ + a₂. Which of the following is a true statement?

A) The code can detect and correct any single-digit error.
B) The code can detect any single-digit error and correct some but not all single-digit errors.
C) The code can detect any single-digit error, but it cannot correct any single-digit error.
D) The code can detect some but not all single-digit errors.