B.the population of the species are reasonably constant over time
Answer:
4
Explanation:
Carbon has four valence electrons, so it can achieve a full outer energy level by forming four covalent bonds. When it bonds only with hydrogen, it forms compounds called hydrocarbons. Carbon can form single, double, or triple covalent bonds with other carbon atoms.
Most canyons were formed by a process of long-time erosion from a plateau or table-land level. The cliffs form because harder rock strata that are resistant to erosion and weathering remain exposed on the valley walls
The 4 classes of biological macromolecules are carbohydrates, lipids, proteins and nucleic acids.
