Which of the following statement is incorrect on resonance ?

Question

$\begin{array}{1 1}(a)\;\text{Resonance leads to extra stability}\\(b)\; \text{Any number of resonance hybrid can be proposed}\\(c)\;\text{The actual structure a hybrid of the various extreme possibilities}\\(d)\;\text{Resonance hybrid is more stable than any one of the constituting structures}\end{array}$