Dichotomous key works on the principle of asking yes-or-no questions about the organism. To identify it, the answers for that organism are then compared to existing organisms to identify it. Prepare a list of four to five questions about each of the organisms listed below to help you create your own key. For each question, make sure the answer isn’t the same for all four organisms. For example, Does the organism have cells? would be an inappropriate question, because all the organisms have cells.

brewer’s yeast (Saccharomyces cerevisiae)
E. coli bacteria (Escherichia coli)
green hydra (Hydra viridissima)
house cat (Felis catus)

Here's the list of questions, the yes-no response for each has been provided under each organism's heading in the same order:

Is it a unicellular organism?

Is it found inside the human body?

Is it visible without a microscope?

Can it produce its own food?

Can it be used in making food?

Brewer’s yeast (Saccharomyces cerevisiae)

Yes

Yes

Yes

No

Yes

E. coli bacteria (Escherichia coli)

Yes

Yes

No

No

No

Green hydra (Hydra viridissima)

No

No

Yes

Yes

No

House cat (Felis catus)

No

No

Yes

No

No

Explanation:

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.