13)
The half-life of carbon-14 is 5730 years. Explain how to figure out the age of a substance that has 25% carbon-14 remaining.
A) Multiply 25% times 5730 years since only 25% of the carbon remains.
B) Divide 5730 years by 2 since carbon has gone through two half-lives.
C) Multiply 5730 years by 2 since two half-lives have gone by for carbon.
Eliminate
D) Multiply 4 times 5730 years since carbon has gone through 4 half-lives.

Multiply 5730 years by 2 since two half-lives have gone by for carbon.

Explanation:

The half-life of a radioactive isotope depicts the measure of time that it takes half of the isotope in an example decay. On account of radiocarbon dating, the half-existence of carbon 14 is 5,730 years  

The half-life of carbon-14 is 5730 years.  

In this manner, after  

1 half-life there is 50 % = 1/2 of the first amount left.  

2 half-lives there is 25 % = 1/4 of the first amount left.  

25% is two half-lives.  

Every 50% of life requires 5730 years.  

So two half-lives require 2 × 5730

answer: the answer is b

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.