In which of the following reactions is a new carbon-carbon bond not formed?

Assertion : Aldol condensation can be catalysed both by acids and bases.
Reason : $\beta$-Hydroxyaldehydes or ketones readily undergo acid-catalysed dehydration.

Which statement is incorrect for the given reaction sequence: $CH_3-CN$ $\xrightarrow[(2) H_2O]{(1) CH_3MgBr} X$ $\xrightarrow{2,4-DNP} Y$?

Which of the following reactants,on reaction with concentrated $NaOH$ followed by acidification,gives the following lactone as the product?

$2CH_3COCH_3 \xrightarrow{Mg/Hg, H^{+}} \text{Product}$,the product in the reaction is:

In the given compounds,which one does not give the silver mirror test?