1) What happened around 10,000 years ago that changed the way many humans live?
A. Humans went from being cave dwellers to roaming hunter-gatherers.
B. Humans went from living on farms to working in factories.
C. Humans went from being roaming hunter-gatherers to settled farmers.
D. Humans invented the spear and became hunters.

Which of the following is not a characteristic of a hydrogen bond? 1. it is responsible for the unusual physical properties of water. 2. it is weaker than a covalent bond. 3. it is stronger than other dipole-dipole interactions. 4. it can occur when hydrogen is covalently bound to very electronegative elements liks f, cl, br and i.