Choose the word that correctly completes the sentence , the security officers checked all nahs and backpacks before allowing them inside the stadium

A. spectators'  

Explanation:

The security officer checked all spectators’ bags and backpacks before allowing then inside the stadium.

Spectators' is the plural of spectator. Spectators' are people or member of an audience that are present at and observe or watch an event or displays such as game. Spectators are also called observers or onlookers.