Which of the following is a feature of osteoporosis?
a. it is most common in men over 45 years of age
b. it has virtually no effect on blood calcium levels
c. it results from short-term deprivation of dietary calcium
d. it causes significant alterations in the blood levels of parathormone and calcitonin
d. it affects about 30 million people in the u. s.

Option A, It is most common in men over 45 years of age

Explanation:

Osteoporosis is caused when the removal of old bone is higher than the creation of new bone . Bones in our body renew continuously and regularly but when a person ages his/her ability to form new bones reduces. Due to this the overall bone mass reduces leading to weaker and porous bone structure. Normally after the age of 30, the capacity to form bones reduces and by the age of early 50s this problem becomes more serious and leads to Osteoporosis.

Thus, option A is correct

one characteristic that is shared by all is a soft body. many

of these invertebrate animals also have an outer shell to protect their

body. oysters, clams, snails, and mussels are all mollusks. so are octopuses, squids, and slugs. mollusks live on land and in freshwater.

igneous rocks which formed by the crystallization of magma at the surface of the earth called extrusive rocks. they are characterized by fine-grained textures because the rapid cooling at or near the surface did not provide enough time for large crystals to grow.