Which are not true? select all that apply.

feudalism is a system of cooperation among peoples which was basically an exchange of gold for protection.
a vassal was given the rights to control the fief and to have ownership of it.
a summons is a call to appear in court.
a knight may serve a vassal in exchange for land.

the conditions that made the byzantine empire vulnerable to attacks by the muslin turks were the sack of constantinople by western crusaders, the conquests of the sultanate of rum, presence of rival kingdoms and finally the set up of fiefdoms at the empire which were owned by the ghazis (turkish warriors).

1. where does the energy of a nuclear power plant come from?

d) political bosses should not hold office