The property which forms the basis of sieving is the difference in
size
Sieving – The method by which the components of a mixture can be separated from each other based on differences in their sizes with the help of a sieve is called sieving.
For example – Fine wheat flour can be separated from coarse flour with a sieve.
The explanation for the correct answer- (A) Size
The difference in size allows only a particular component to pass through the holes of the sieve.
The explanation for incorrect answers -
(B) Colour - it forms the basis of separation for hand-picking.
(C) Weight - it forms the basis of separation for winnowing.
(D) Shape - it forms the basis of separation for hand-picking.
hence, option (A) is correct. The property which forms the basis of sieving is the difference in size.