What contributed did jonas salk make to science in the 1950s a. he invented ddt, the miracle pesticide b. he designed the first us satellite. c. he developed smaller computers. d. he created a vaccine against polio so much

How did inca develop their road system? a) they used mortar to hold the stones together.b) they built suspension bridges over rivers. c) they mixed copper and stone together to make the blocks.d) they laid roads in the cities, not in the less densely populated deserts.