Which of the following statements about cellular aging is true?
a. damage is caused by free radicals that slow down the cell-duplication process.
b. cells can replicate indefinitely, but errors do occur.
c. aging may be caused by the inevitable loss of the ability of cells to duplicate perfectly.
d. cells from adults are able to duplicate more quickly and more times than are cells from embryos.

a. Damage is caused by free radicals that slow down the cell-duplication process.

c. Aging may be caused by the inevitable loss of the ability of cells to duplicate perfectly.

Explanation:

The free radical theory of aging states that aging is caused by accumulation of damage inflicted by reactive oxygen species (free radicals).  It proposes that organisms age because they accumulate oxidative damage, Now,this damage comes from reactive oxygen species (ROS), which are partially reduced metabolites of molecular oxygen (free radicals) generated as products of metabolic reactions. Thus,  these free radicals cause damage that slow down the cell-duplication process.

Also, Aging may be caused by the inevitable loss of the ability of cells to duplicate perfectly. (SENESCENCE).

When senescence occurs (i.e inevitable loss of the ability of cells to duplicate perfectly) there is  progressive deterioration of physiological function, an intrinsic age-related process of loss of viability and increase in vulnerability of cells.

the major parts of the digestive system:

salivary glands.

pharynx.

esophagus.

stomach.

small intestine.

large intestine.

rectum.

accessory digestive organs: liver, gallbladder, pancreas.

it is a limiting nutrient limited by a single nutrient in the ecosystem, & the single goes very slow.