Why do recommendations for vitamin d intake increase in later adulthood?
a. older individuals cannot absorb this vitamin from fortified milk.
b. the rate of bone mineralization increases after age 45.
c. more vitamin d is excreted by the kidney with age.
d. synthesis of this vitamin decreases with age.

The synthesis of Vitamin D decreases with age. This is due because of a fall in 7-dehydrocholesterol levels.

Smoking damages the respiratory system by inhalation of a foreign substance, that is absorbed and residue is left behind on our lungs sponge like substance. the gas that is inhaled also increase your blood pressure and dilates your blood vessels. also the process of inhaling and exhaling the smoke it causes irritation to the throat and mouth. smoking can cause lung cancer and other respiratory and circulatory diseases.