Answer
The rope tied to the tree sustains greater tension.
Work Step by Step
In the tug-of-war game, the tension in the rope $T$ is caused by the pulling force that each team of 5 people exerts on the rope. Since there are 2 teams pulling in opposite directions, there are 2 tension forces in equal magnitude but opposite direction balancing each other.
When the rope is tied to the tree and pulled by 2 teams, the tension in the rope is caused by the pulling force that 10 people exert on the rope. It is obvious that the rope in this case sustains greater tension.
