Milk fever is caused due to the deficiency of?

Correct option is A

Milk fever, also known as hypocalcemia, is a condition in lactating animals, particularly dairy cows, caused by a deficiency of calcium (Ca). It commonly occurs around the time of calving when the demand for calcium is high due to milk production. The insufficient intake or absorption of calcium from the diet can lead to milk fever. It is a significant concern in dairy farming and is usually addressed through dietary supplementation to prevent and manage the condition in lactating animals.