Identify the product C in the series

An unknown compound ‘D’ first oxidised to aldehyde and then acetic acid by a dilute solution of K₂Cr₂O₇ and H₂SO₄.The compound ‘D’ is:

Suggest appropriate structures for the missing final compound. (The number of carbon atom remains the same throughout the reaction)

Clemmensen’s reduction of ketones is carried out in :

A compound X of formula C₃H₈O yields a ketone C₃H₆O on oxidation.To which of the following class of compounds would X belong?

Which of the following gases does not form a ketone on treatment with dil H₂SO₄ and 1% HgSO₄ ?

Two molecules of acetic acid on heating with phosphorous pentoxide produce :

A new C — C bond is formed in :

Reaction of phenylacetylene with dil. H₂SO₄ and HgSO₄ gives

Benzaldehyde and alcohol KCN reacts to produce which of the following :