What is the opportunity cost of a decision?

Children begin to use tools at about what age? a. 18 months b. 2 years c. 1 year d. 6 months

What were the death camps? who was sent there?

What was the name of the theory that said that if one country in a region fell to communism, others would surely follow? 1) domino theory 2) arms race 3) brinkmanship 4) containment theory