How would you name the following compounds?
$(i)$ $CH_{3}-CH_{2}-CH=CH_{2}$
$(ii)$ $CH_{3}-CH_{2}-CH_{2}-C(CH_{3})_{2}-CH_{3}$
$(iii)$ $CH_{3}-CH_{2}-CHO$
$(iv)$ $CH_{3}-CH(OH)-CH_{3}$

(A-D) $(i)$ The compound $CH_{3}-CH_{2}-CH=CH_{2}$ has four carbon atoms and a double bond,so it is named But-$1$-ene.
$(ii)$ The compound $CH_{3}-CH_{2}-CH_{2}-C(CH_{3})_{2}-CH_{3}$ has a five-carbon chain with two methyl groups at the second position from the end,so it is named $2,2$-Dimethylpentane.
$(iii)$ The compound $CH_{3}-CH_{2}-CHO$ has three carbon atoms and an aldehyde functional group,so it is named Propanal.
$(iv)$ The compound $CH_{3}-CH(OH)-CH_{3}$ has three carbon atoms and an alcohol functional group at the second carbon,so it is named Propan-$2$-ol.