My question is how do you know all this ?

What are the main functions of the human skeleton? a exchange of gases b support and movement c sensing the environment d digestion and excretion

This is an ap world history question. i am working on a worksheet which has a vent diagram with each circle labeled either us or byzantine economy. the middle is the similarities. can someone explain to me the similarities and especially the differences between the two?

Which of the following properties of a soil sample most influences the flow of water through the sample a. colorb. fertilityc. permeability d. phe. salinity