1. Feudalism is a system of cooperation among peoples which was basically an exchange of gold for protection.
2. A vassal was given the rights to control the fief and to have ownership of it.
3. A summons is a call to appear in court.
4. A knight may serve a vassal in exchange for land.
The best and most correct answers among the choices provided by the question are the first choice or number 1, and the fourth choice or number 4.
Feudalism is a system of cooperation among peoples which was basically an exchange of gold for protection and a knight may serve a vassal in exchange for land are statements that are not true.
I hope my answers has come to your help. God bless and have a nice day ahead!