Hey there!
Airplanes must be pressurized when flying at high altitudes so that the oxygen levels stay normal for us to breathe. The higher you go up, the thinner the air gets, which causes breathing problems for us humans.
Thank you!
The panama was the important country for the Inca's.
:)
XD
Rome was one of the richest and protected cities, and I can see there two correct options. I bet one than more is acceptable, so B.
Rome was built on seven hills, which offered natural protection from invaders. and D.
The climate of Rome was good for growing a variety of crops. are the truthful reasons why this city has a good site.
B is correct because the others are wrong, c is wrong because the reason they have varying states of matter is because pressure and a is wrong because mantle
