The four pulmonary veins return oxygenated blood to this chamber. What is this chamber?

*will mark brainliest to first correct answer* photosynthesis led to increasing levels during the later proterozoic eon? a. oxygen b. water c. carbon dioxide d. none of the above

Each hereditary trait corresponds to

Why do some dna fragments move farther than others during gel electrophoresis? a. because their shapes are different b. because they are different types of molecules c. because the samples are different colors d. because their masses are different