Two of the nitrogen bases are single structures know as pyrimidines

Some tools have graduations to show multiple measurements. for example, a ruler may have graduations for both millimeters and centimeters. when measuring the length of an earthworm, which graduations would allow for the most accurate measurement? millimeters centimeters decimeters meters

What is the difference between a scientific hypotheses and a scientific theory?

Pulmonary arteries carry highly oxygenated blood. true or false?