What must be true for players to be able to share resources in a Two-Headed Giant game?

In Two-Headed Giant games, players are organized into teams where each team consists of two players working together. For players to share resources effectively, they must be on the same team. This team dynamic allows for cooperative strategies, including sharing life totals and combining efforts to defeat the opposing team.

This collaborative framework emphasizes working together to achieve a common goal, which is fundamental to the Two-Headed Giant format. Players can tap into shared resources such as cards in hand, mana available, and other in-game actions that can benefit each other, which is not possible if they were on opposing teams.

The other possible choices do not align with the rules governing Two-Headed Giant. Players do indeed need to be in the same location to physically interact with the game, but that's not a requirement specific to sharing resources. Similarly, it is not necessary for players to be in full control of the game to share resources; they can do so even when circumstances are challenging. Lastly, being from different teams contradicts the basic team concept of the format.