Why did trade along the silk road flourish during the time of han, kushan , parthian , and roman empire

Why are low-lying lands more suitable for agriculture than hilly areas?

This cartoon appeared in 1916. the topic of the cartoon isa)the reason for the start of world war i.b)the success of us submarines in world war i.c)the military alliance between germany and mexico.d)the attitude in the us towards submarine warfare in world 

Which act was a response to three high-profile assassinations? a. the mailing of firearms act b. the national firearms act c. the gun control act d. the brady handgun violence prevention act