Answer
Please see the work below.
Work Step by Step
We know that
a. Addition of an acidic solution of dechromate ionto acetaldehyde will cause the reagent to change from orange to green as the aldehyde is oxidized.
b. Addition of a solution of $Br_2$ in $CCl_4$ to 2-methyl-cyclohexene will cause the bromine color to disappear because the dibromomethlycyclohexe is formed.