ทำไมใช้ Present Perfect

An agency has appointed or hired people who run a department. The Department of Energy is an agency. The head is appointed as an “agent” of the government.

An administration is run by elected officials who follow laws and rules to run things, so “administer” the law. The Presidency is an administration to run the country.

An authority is an organization to enforce rules: they have the “authority” to fine and arrest people. The police are authorities. The military are NOT authorities.

-ทำไมเขาใช้ Present Perfect ไม่ใช้ Present simple ในประโยค An agency has appointed or hired people who run a department. ใครรู้รบกวนช่วยอธิบายให้ฟังหน่อยนะครับ?