Consider the coordination compound , $\;[CO(NH_{3})_{6}]Cl_{3}\;$ . In the information of this complex , the species which acts as the Lewis acid is :

Question

$(a)\;[Co(NH_{3})_{6}]^{3+}\qquad(b)\;Cl^{-}\qquad(c)\;Co^{3+}\qquad(d)\;NH_{3}$