Which of the following reagents will convert glycerol into acrolein?

For the following compounds,write structural formulas and $IUPAC$ names for all possible isomers having the number of double or triple bonds as indicated:
$(a)$ $C_4H_8$ (one double bond)
$(b)$ $C_5H_8$ (one triple bond)

Identify the product $B$ in the following reaction sequence:
$1,4-\text{cyclohexadiene-1,4-dicarboxylic acid}$ $\xrightarrow{NaOH} A$ $\xrightarrow{\text{Kolbe electrolysis}} B$

The product of the above reaction will be:

The number of possible products for $x$ and $y$ is

$CH_2(COOH)_2 \xrightarrow{P_4O_{10}, \, 150^\circ C} X$
Compound $(X)$ is