To solve this problem, we need to understand the composition of Fehling's solution.$\newline$Fehling's solution is used in qualitative analysis to test for reducing sugars. It consists of two separate solutions:$\newline$• Fehling's solution A: This is an aqueous solution of copper(II) sulfate (CuSO$_4). \newline$• Fehling's solution B: This is an alkaline solution containing sodium potassium tartrate (Rochelle's salt) and sodium hydroxide (NaOH).$\newline$When these two solutions are mixed, the copper(II) ions from Fehling's solution A form a complex with the tartrate ions from Fehling's solution B.$\newline$The correct option for Fehling's solution A is:$\newline$Option 3: Aqueous copper sulphate.