In the case of Giffen good like bajra, a fall in its price tends to-

The correct answer is: B. reduce the demand.

A Giffen good is a good for which the demand increases as the price increases. This is because the good is a necessity for the consumer and they are willing to pay more for it as their income decreases. In the case of bajra, a fall in its price would make it less affordable for low-income consumers, who would then switch to other, cheaper foods. This would lead to a decrease in the demand for bajra.

Option A is incorrect because the demand for a Giffen good does not remain constant as the price changes.

Option C is incorrect because the demand for a Giffen good decreases as the price decreases.

Option D is incorrect because the demand for a Giffen good changes in an abnormal way, as opposed to the normal way in which demand changes with price.