The correct answer is (d) caseins. Caseins are the main proteins in milk, and they are responsible for its white color. When milk is exposed to light, the caseins scatter the light in all directions, which gives milk its white appearance.
Lactose is the sugar in milk, and it is not responsible for its white color. Albumins are proteins that are found in milk, but they are not as abundant as caseins. Carotenes are pigments that are found in plants, and they are not found in milk.
Here is a more detailed explanation of each option:
(a) Lactose is the sugar in milk. It is a disaccharide, which means that it is made up of two sugar molecules: glucose and galactose. Lactose is not responsible for the white color of milk.
(b) Albumins are proteins that are found in milk. They are globular proteins, which means that they have a spherical shape. Albumins are not as abundant as caseins, and they are not responsible for the white color of milk.
(c) Carotenes are pigments that are found in plants. They are responsible for the orange color of carrots, pumpkins, and other fruits and vegetables. Carotenes are not found in milk, and they are not responsible for its white color.
(d) Caseins are the main proteins in milk. They are globular proteins, and they are responsible for the white color of milk. When milk is exposed to light, the caseins scatter the light in all directions, which gives milk its white appearance.