Which of the following carbonyl compounds does $NOT$ undergo aldol condensation?

Consider the following reactions:
$A$ $\xrightarrow[(i) CH_3MgBr]{(ii) H_3O^{+}} B$ $\xrightarrow[573 \text{ K}]{Cu} 2\text{-methyl-2-butene}$
The mass percentage of carbon in $A$ is:

Wolff-Kishner reduction reduces which of the following groups?

In the Cannizzaro reaction,the intermediate that will be the best hydride donor is:

For the reaction given below:
The compound which is not formed as a product in the reaction is a:

An organic compound $x$ where the molar ratio of $C$, $O$, and $H$ are equal, on treatment with $50\% \ KOH$ under reflux followed by acidification produced $y$. The most likely structure of $y$ is: [Molar mass of $x$ is $58 \ g \ mol^{-1}$]