The greatest factor in the development of "skyscrapers" was a) the invention of elevators. b) availability of cheap iron. c) the invention of escalators. eliminate d) recovery from the great depression.

How do you think entrepreneurs contribute or industry in america? describe your answer.

"if i have seen farther than others," said newton, "it is because i have stood on the shoulders of giants." who were the giants to whom newton was referring? could this be said of any scientific accomplishment? explain.

What was one major cause of worldwide conflict during the first decade of the 21st century?