Question

To increase milk yield, a cow is given _______.
a) Sorbitol
b) Stilbestrol
c) Prolactin
d) Gonadotrophin

Answer 1

Lactation is the process of secretion of milk. It is a temporary process that starts from the last month of pregnancy until a few months of delivering the newborn. It is typical to the female individuals (mother) of a species.

Complete answer
Scientists have developed many synthetic serums that have the ability to initiate this lactation process in a cow body even without pregnancy for a prolonged period of time. Many farmers use such synthetic serums to increase milk production of their cows.
Sorbitol is a kind of sugar alcohol found naturally in fruits. It is unhealthy as it is involved in retaining water from the body in excessive amounts causing serious health issues. Therefore, it is nowhere related to lactation thus is an incorrect option.
Stilbestrol is a kind of synthetic serum consisting of oestrogen. It initiates the process of lactation in the mother body right after 30 days of injection in the body. It is commonly used by farmers for increasing milk production of their cows. Thus, it is the correct option.
Prolactin is a hormone produced by the pituitary gland in the human body. It initiates production of milk in the female body. As it is concerned with milk production in humans thus it is an incorrect option.
Gonadotropins are a kind of hormone secreted in humans after puberty. They initiate the sex organs to grow and start their reproductive processes. Thus, they are nowhere related to milk production. Hence, it is an incorrect option.

Therefore the correct answer is option b) Stilbestrol.

Note:
Cows are viewed as one of the largest sources of milk all over the world. Thus, are commonly used by dairy farmers (those involved in the business of trading milk and milk products) as a source of income. As cows are also mammals, so, like all other mammals, cows also have a limited period of lactation preceded by pregnancy. This limits the economy of dairy farmers.