Biologists working in Spain say that their discovery of teeming life in a highly acidic river may not only broaden the search for life, or for evidence of past life, no other planets but also show that a number of forms of microscopic life can adapt to conditions that scientists have long thought hostile to all but the hardiest bacteria.

A. show that a number of forms of microscopic life can adapt to conditions that scientists have long thought hostile to all but the hardiest bacteria
Broaden is plural and hence the show is plural which is correct.
B. may show that a number of forms of microscopic life is capable of adapting to conditions that scientists have long thought hostile to all bacteria but the hardiest ones
may broaden and may show is not correct especially if may comes after but also.
C. shows a number of forms of microscopic life to be capable to adapt to conditions that scientists have long thought had been hostile to all but the hardiest bacteria
may not only broaden (plural) should be accompanied with show and not shows (singular)
D. showing that a number of forms of microscopic life is capable of adapting to conditions that scientists have long thought had been hostile to all but the hardiest bacteria
may not only broaden and showing are not parallel
E. showing that a number of forms of microscopic life can adapt to conditions that scientists have long thought hostile to all bacteria but the hardiest

This correct option is A.

Explanation:

The question requires sentence correction "show that a number of forms of microscopic life can adapt to conditions that scientists have long thought hostile to all but the hardiest bacteria"

Using typical parallelism as key to show that the right option are grammatically identical or similar in structure, sound, meaning, or meter and so on.

The answer A showed parallelism by having a structure that tactically showed "not only" and "but also" in the sentence.

Keyword 'broaden" is the verb original form in the context and was added behind "not only", in the options the verb original form show was added after "but" .

So Option B, Option C, Option D, and Option E can be excluded.

We see that a "not only" plus "but" is needed to ensure that the two phrases are connected in parallel

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.