Question

Hand picking is preferred when
(a) the quantity of the mixture is small
(b) the unwanted substance is present in large quantities
(c) the unwanted substance can dissolve
(d) the size or colour of the unwanted substance is the same as the useful one

Answer 1

(a) the quantity of the mixture is small

Hand-picking is preferred when the quantity of the mixture is small, the unwanted substance is present in smaller quantities, and the size, shape and colour of the unwanted substance are different from those of the useful one.