In MARS you can challenge other players in exchange for their buildings. Both players will perform the same test of five questions, the one who answers the most correctly in the shortest time possible wins.
In case there is a draw the player who has answered the quickest wins. In an unlikely event that both players answer the same number of questions at the same time, the winner will be the player defending their building, the one being challenged.
Keep in mind that all of the questions that appear in a challenge are "Certified Questions" so they will never be incorrectly formulated.