Which of the following has the most acidic hydrogen?

The reagent used in Wolff-Kishner reduction is

In the given reaction,what is $y$?
$CH_3CH_2COCH_2COOH$ $\xrightarrow{\Delta} x$ $\xrightarrow[(ii) H_2O]{(i) LiAlH_4} y$

Compound $A$ (molecular formula $C_3H_8O$) is treated with acidified potassium dichromate to form a product $B$ (molecular formula $C_3H_6O$). $B$ forms a shining silver mirror on warming with ammoniacal silver nitrate,and $B$ when treated with an aqueous solution of $NH_2NHCONH_2$ and sodium acetate gives a product $C$. Identify the structure of $C$.

The correct order of decreasing value of $K_{eq.}$ for the addition of $HCN$ to the following carbonyl compounds is:

Reactant	$K_{eq.}$
$PhCHO$	$a$
$CH_3CH_2COCH_3$	$b$
$PhCOCH_3$	$c$
$CH_3CHO$	$d$

The major product of the following reaction is