Which one of the following statements regarding ‘Root locus’ is not correct?

• A. By the addition of poles to the left half, the root locus shifts towards the right-hand side, and the stability of the system decreases
• B. By addition of zero towards left, the root locus shifts towards left half, since root locus shifts towards left half, the relative stability of control system increases
• C. By the addition of zero towards the left side, the root locus shifts towards the left half, the relative stability remains the same
• D. By addition of poles to the left half, the system stability decreases, while by addition of zeros towards left half, the stability of system increases