Lots of ! how many years did it take the modern engineers to figure out how the roman concrete was made out of? pls give me the accurate number, its for a !

Which term do historians use to describe the personal preferences that people have that affect their interpretation of events

The bloodless, or glorious, revolution in 1688 a. encouraged nobles in their quest to recreate a feudal society. b. ended the commonwealth and restored james ii to the throne. c. placed mary and william, both protestants, on the throne. d. restored property rights to those who had lost them as a consequence of the english civil war.

What are some inventions during the han dynasty?