In the 1950s, the polio virus paralyzed many children for life. Today, polio has been reduced by 99 percent. Which of the following has played the greatest
role in reducing polio infections worldwide?
A. Agriculture
B. Cooperation
C. Education
D. Consumption

“there he took part in the conquest of cuba. the spanish government gave him land and slaves in return for his service… eventually, he settled down on a plantation. but he was restless, and still far from wealthy. in fact, he was in debt. what money he had, he squandered on gambling, expensive clothes, and nights out on the town. then his luck turned. spanish sailors landed on the yucatan peninsula of mexico and sent back word of an extraordinary find… rumors of a land filled with gold… cortes leaped at the chance for gold and glory… velazquez, the spanish governor, grew troubled and sent orders forbidding [cortes] to sail. but cortes was not about to lose this opportunity. under the cover of darkness, he raised anchor and slipped from port.” how did cortes lose what money he had before he set sail for mexico? a he put all his money into a business that declared bankruptcy. b he spent it on fancy clothes, gambling, and having fun. c he gave it away to charity. d it was stolen from him.