Study the image, which describes how rapid changes in weather conditions occur.

How rapid changes in weather conditions occur. Arrow labeled Direction of frontal movement points right toward Cold front map symbol. Arrow labeled Rising warm air in front of cold front points from cold front to sky. Also labeled are: Development of clouds because of upward movement of warm air, and Advancing cold air behind cold front.

Based on the arrows, what does the image represent?

Air masses are barely moving.
Air masses are colliding with each other.
Jet streams are forming in the upper atmosphere.
Weather conditions are remaining steady and unchanged.

for many centuries there were important factors which the economies of the muslim empires developed increasingly. they applied economic procedures in production, investment, finance, taxation and property. they used to tax certain goods (for example: harvest), they charged interest on money lent, they signed contracts with merchants; they relied on a common currency, and they used checks as well as promissory notes. with the money collected by means of taxation, the government provided the needy with an income. in addition, trading networks covered huge distances, so far regions started to have contact and exchange goods. this trade network covered areas of asia, africa and europe.