Typical seawater has a salinity of 35 psu (practical salinity units). In which month is the difference in salinity of surface and bottom waters the greatest? Why do you think the difference is the greatest at this time of year?

2pi more meters because you find the circumference which is 6pi and 4pi and subtract it and you get 2pi

I'm guessing  a. diverse  because it shows a wide variety of many things.

They contributed many things, but here are some examples:

1) democracy - democracy as a political system was first implemented in ancient athens
2) some advances in mathematics - such as the pythagoras' law
3) the script - the roman script was adopted from ancient greek.