(a)
$CH_{3}CH_{2}CH_{2}OH\underset{H_{2}So_{4}}{\overset{\ \ K_{2}{Cr}_{2}O_{7}\ \ \ \ }{\rightarrow}}CH_{3}CH_{2}CHO$
(B )
propanol propanal
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \overset{H_{2}NCONHNH_{2}}{\rightarrow}CH_{3}CH_{2}CH = NNHCONH_{2}$
(C)