Why is oxygen a molecule but not a compound? a) it only contains atoms of single elements b) it contains atoms from different elements c) oxygen can''t form compounds d) only ions form compounds

When does the circulatory system work with the respiratory system? a. during blood cell formation b. during cellular respiration c. during intestinal digestion d. during a viral infection

Which statement describes the punctuated equilibrium theory?

Fossils of ancestors of the modern horses show a small 4-toed almost dog-like browsing animal named eohippus over time the horses got larger lost toes and changed to a grazing diet what is the best explanation of why this change occurred