Which of the following oxide is basic in nature

Find the odd one out and explain your choice:

$\mathrm{A}: \mathrm{Al}(\mathrm{OH}{)}_3, \mathrm{B}: \mathrm{Pb}(\mathrm{OH}{)}_2, \mathrm{C}: \mathrm{Mg}(\mathrm{OH}{)}_2$ and $\mathrm{D}: \mathrm{Zn}(\mathrm{OH}{)}_2$. (Enter your correct answer as $\mathrm{A}, \mathrm{B}, \mathrm{C} \mathrm{or} \mathrm{D}$)

Write balanced chemical equation for the following reaction:

When sodium hydroxide is added to copper sulphate.

Name the following:

A basic oxide which is insoluble in water. 

Give one important use of the ammonium hydroxide base.

Name the following:

A base used in softening hard water.

Give the balanced chemical equation for the action of $\mathrm{KOH}$on ${\mathrm{ZnSO}}_4$.