When aldehydes or ketones are treated with $C_6H_5-NH-NH_2$ (phenylhydrazine),the product formed is:

The general name of the compound formed by the reaction between aldehyde and alcohol is

Assertion : Benzaldehyde is more reactive than ethanol towards nucleophilic attack.
Reason : The overall effect of $-I$ and $+R$ effect of phenyl group decreases the electron density on the carbon atom of $>C=O$ group in benzaldehyde.

Which of the following compounds will give a silver mirror test with ammoniacal silver nitrate (Tollens' reagent)?
$(A)$ Formic acid
$(B)$ Formaldehyde
$(C)$ Benzaldehyde
$(D)$ Acetone
Choose the correct answer from the options given below:

Complete reaction of acetaldehyde with excess formaldehyde,upon heating with conc. $NaOH$ solution,gives $P$ and $Q$. Compound $P$ does not give Tollens' test,whereas $Q$ on acidification gives positive Tollens' test. Treatment of $P$ with excess cyclohexanone in the presence of catalytic amount of $p$-toluenesulfonic acid $(PTSA)$ gives product $R$. Sum of the number of methylene groups $(-CH_2-)$ and oxygen atoms in $R$ is....

The end product $(C)$ of the reaction is: