How did the nearby deserts and mountains affect life in ancient China?

Which of the following was an economic reason for the united states to declare war on spain in 1898?

Journey stations were established throughout the mongol empire every miles.

24-karat gold is considered to be pure gold. 18-karat gold is considered to be about 75% gold. what is 18-karat gold considered a mixture rather than a pure substance? a) it has a variable composition of other elements and minerals. b) its color is different than pure gold. c) the gold atoms are not arranged in a repeating pattern. d) it can be melted and transformed into a different substance.