Explain any two methods of Preparation of aldehydes.

Question

$\begin{array}{1 1} \text{(a) (i) Dehydrogenation of alcohols (ii) By oxidation of alcohols} \\ \text{(b)(i) Dehydrogenation of Acetic Acid (ii) By oxidation of alcohols} \\ \text{(c) (i) Halogenation of alcohols (ii) By Reduction of alcohols} \\ \text{(d) (i) By ozonolysis of alkanes (ii) By hydration of Acids}\end{array}$