Explain Werner’s Theory

Question

$\begin{array}{1 1} \text{(a)The central metal or the metal atoms in coordination compounds show four types of valency.} \\ \text{(b)The central metal or the metal atoms in coordination compounds show two types of valency.} \\ \text{(c)The metal in coordination compounds show multiple types of valency.} \\ \text{(d)The central metal or the metal atoms in coordination compounds show three types of valency.}\end{array}$