Hydrogenation of the compound shown below in the presence of a poisoned palladium catalyst (Lindlar's catalyst) gives:

Which is the most acidic of the following?

Maximum bond energy of $C-H$ bonds is found in the compound:

Which of the following compounds forms a $Na$-salt upon reaction with $NaNH_2$?

$CH_3-C \equiv C-O-CH_3 \xrightarrow{dil. H_2SO_4, HgSO_4} \text{major product}$

An organic compound $X$ with molecular formula $C_6H_{10}$,when treated with $HBr$,forms a $gem$-dibromide. The compound $X$ upon warming with $HgSO_4$ and dil. $H_2SO_4$,produces a ketone,which gives a positive iodoform test. The compound $X$ is