Fehling's solution is a chemical reagent used to differentiate between water-soluble carbohydrates and ketone-functional groups, and as a test for monosaccharides. It is used specially in the Fehling's test for reducing sugars. The test involves two solutions, generally known as Fehling's A and Fehling's B, which are mixed together and added to perform the test.

Fehling's solution 'A' is an aqueous solution of copper(II) sulfate. Thus, the correct option is:

Option A: aqueous copper sulphate

The function of Fehling's A is to provide copper(II) ions, $ Cu^{2+} $, which act as the oxidizing agent in the reaction with the reducing sugar. When Fehling's Solution A and B are mixed and heated with a reducing sugar, the copper(II) ions are reduced to copper(I) oxide, which precipitates as a red solid, indicating a positive result.

Fehling's Solution B, on the other hand, contains alkaline sodium potassium tartrate, which helps to maintain the solution in an alkaline condition and keeps the copper(II) ions in solution.

Thus, in summary, Fehling's A consists of aqueous copper sulfate, which directly matches with Option A.