Option (A) is the correct answer because, ligases are the enzymes that catalyse the linking together of 2 compounds, e.g., enzymes which catalyse joining of C – O, C – S, C – N, P – O etc. bonds.

$\Rightarrow$ Options (B), (C) and (D) are wrong as ligase catalyse the joining of P – O, C – O & C – N bonds.