1. Why does the moon appear to change throughout each month? * a. The fraction of the moon that is lit by the sun changes.
b. Different parts of the moon become visible from Earth as the moon rotates
c. Different parts of the sunlit area are visible from Earth due to motions in the Earth-sun-moon system.

C

Explanation:

As the Earth moves in relative to the moon the Earth blocks part of the sun from the moon causing only parts of the moon to light up. This BEST answers the question because B is not accurate because it doesn't describe why we actually SEE it. A might be true but it is not the BEST explained.

Hope this helps! (^-^)

hypoxemia refers to a below usual concentration of oxygen in the blood, mainly in the arteries. hypoxemia is an indication of an issue associated with circulation or breathing and may lead to various symptoms like shortness of breath.  

the condition is identified by determining the level of oxygen in the blood sample obtained from an artery. it can also be predicted by determining the oxygen saturation of the blood with the application of a pulse oximeter.  

the normal arterial oxygen is about 75 to 100 mm hg. the values underneath 60 mm hg is generally considered with the requirement for supplemental oxygen. the normal pulse oximeter readings generally range between 95 to 100 percent. the values under 90 percent are regarded as low.  

in the given case, the oxygen saturation is measured at 93 percent, hence, there is no need to administer oxygen, that is, one should withhold oxygen.