PLEASE HELP Two factors that affect human sleep patterns are the time of day and level of melatonin, a chemical found in one's body. For example, as the Sun goes down at night, the body knows it is time to go to sleep. Similarly, when a person's level of melatonin changes, they can become alert or sleepy. Using this information, how could these stimuli be described?

A. Hours of sunlight per day and melatonin levels are both Internal stimuli.

B. Hours of sunlight per day and melatonin levels are both external stimull.

C. Hours of sunlight per day is an external stimulus, while the level of melatonin in a person is an internal stimulus.

D. Hours of sunlight per day is an internal stimulus, while the level of melatonin in a person is an external stimulus.

E. Hours of sunlight per day and melatonin levels are both internal and external stimuli.

answer: carbon 14 can only be used to determine the age of the organisms that were once living, and igneous rocks are non living.

explanation:

carbon 14 dating is used to determine the age of the sample by estimating the amount of carbon 14 present in the sample and then comparing it with a reference standard.carbon 14 is a isotope of carbon which is radioactive and unstable. carbon 14 is assimilated by all plants and animals throughout their life from carbon dioxide. however, one the organisms die they stop this assimilation and the carbon 14 content starts to decrease.by knowing how much of carbon 14 is left in an organism after his death, one can estimate the age of the organism. the materials whose age can be estimated by carbon 14 method are the organic compounds. however, some inorganic compounds such as aragonite   shell can also be dated.however, if we consider the igneous rocks it is a non living component which never accumulated carbon 14 in it and thus, we cannot use carbon 14 dating method to estimate its age.

C. a mature ovule of a plant.