If Early Earthʹs Atmosphere Contained Little or No O2, Then

question 13

Multiple Choice

If early Earthʹs atmosphere contained little or no O2, then where did most of the O2 in our modern atmosphere come from?

• A) Respiration
• B) The splitting of water vapor by sunlight
• C) The breakdown of carbon dioxide
• D) Photosynthesis
• E) The oxidation of metals

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Definitions:

Digital Rectal Exam

A physical examination method where a healthcare provider inserts a gloved, lubricated finger into the rectum to check for abnormalities.

Biopsy-Proven

Confirmation of a disease or condition by examining a tissue sample removed from a patient's body.

Sensitivity

The ability of a test to correctly identify those with the disease (true positive rate), indicating its reliability in detecting cases.

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