o-Xylene on ozonolysis gives

Question

$\begin{array}{1 1}(a)\;\text{A mixture of one mole of glyoxal and two moles of methyl glyoxal}\\(b)\;\text{A mixture of two moles of glyoxal and one mole of dimethyl glyoxal}\\(c)\;\text{A mixture of two moles of dimethyl glyoxal and one mole of glyoxal}\\(d)\;\text{Both (a) and (b)}\end{array}$