Wheat flour can be separated from the wheat bran by:
A.) hand picking
B.) sieving
C.) winnowing
D.) filtration

Hint: The wheat flour can be separated from the wheat bran because of the different sizes of wheat flour and wheat bran. The size of the wheat flour is less than that of the size of the wheat bran.

Complete step by step answer:
As we know that to separate different substances from a mixture which contains two or more types of substance in it, we can use many methods based on what type of the mixture is given. In the given mixture, the wheat bran is the outer layer of the cereal grain.
For option A.), the handpicking is used to separate those mixtures in which the components differ in their size, shape and color. But as we know that the wheat flour and wheat bran are similar in color and are so small that we cannot separate them easily by hand picking.
For option B.), the sieving is the method used when the components of the mixture are different in their sizes. As we know that wheat flour particles are finer than the wheat busk. So, wheat flour passes through the sieve and the bigger size wheat bran particles stay on the sieve. Therefore, sieving is used for the separation of wheat flour and bran.
For option C.), the winnowing is the process of separation that can be used when the weight of the constituents in a mixture differs from each other. But as we know that wheat flour and wheat bran does not have considerable weight difference. Therefore, this method cannot be used for the separation of wheat flour and wheat bran.
For option D.), the filtration is the process used for the separation of particles from fluid. This fluid may be a liquid or a gas. But as we know that wheat flour and wheat bran both are solid particles so they cannot be separated by the process of filtration.

Hence, option B.) is the correct answer.

Note:
Always remember that sieving method of separation of particles is used when the particles of a mixture is different from each other on the basis of weight like in wheat from husk. And sieving is used to separate particles having different sizes.