Are there any parts of the human body that get oxygen directly from the air and not from the blood?

The cornea in the eye.

Explanation:

The cornea is the only part of a human body that has no blood supply; it gets oxygen directly through the air.  The cornea is a transparent tissue, allowing for light to pass through. If it had blood vessels there, that would be an issue - for that tissue! And the cornea receives its oxygen directly from the air. When contact lenses were first used, people were instructed to take out their contacts when they go to sleep - because wearing them at night would reduce the oxygen intake to the eyes. Then they began manufacturing contact lenses that allowed for the lenses to “breathe” permitting people to wear them day and night.

a tetrad is the foursome during meiosis made by two homologous chromosomes that have each already replicated into a pair of sister chromatids.

hey, i believe your answer would be d. sugar ribose and the base uracil. i believe this is the answer, because rna consists of sugar ribose, adenine, guanine, cytosine, and uracil.

your first option is incorrect, because that's dna. where it consists of sugar deoxyribose, adenine, guanine, cytosine and thymine.

your second option is also incorrect, this is because sugar deoxyribose is in dna, and uracil is in rna. these two do not make sense together.

your third option being incorrect, because sugar ribose is in rna, but not the base of thymine. rna consists of uracil, not thymine.

lastly your fourth option being correct! this answer is correct, because both sugar ribose, and the base uracil are in rna! ~

answer is d. sugar ribose and the base uracil.