Assertion (A):All aliphatic aldehydes give a positive Fehling's test. True.They reduce Fehling’s solution to give a brick-red precipitate of $\mathrm{Cu_2O}$.Reason (R):“Aliphatic aldehydes are reduced by Fehling’s reagent.” False.Actually, aldehydes are oxidized, not reduced.Aldehyde $\rightarrow$ oxidized to carboxylate ion$\mathrm{Cu}^{2+}$ (in Fehling’s solution) $\rightarrow$ reduced to $\mathrm{Cu_2O}$So the aldehyde acts as a reducing agent.