Final answer:
OCO-3 measures global carbon dioxide levels using satellite-based observations by detecting CO2's infrared signatures.
Step-by-step explanation:
OCO-3, or the Orbiting Carbon Observatory-3, measures carbon dioxide concentrations across the globe using B) satellite-based observations. This sophisticated instrument is attached to the International Space Station and utilizes high-resolution spectrometers to detect the unique infrared signatures of carbon dioxide. By observing the sunlight reflected off the Earth's surface, OCO-3 can accurately measure CO2 levels and map them across the planet to study changes in atmospheric composition over time.