In what order do you apply multiple effects within layers 1 through 6?

The correct choice highlights the systematic approach to applying effects within the layers of the rules. In Magic: The Gathering, when multiple effects interact within layers 1 through 6, the order in which they are applied matters significantly and follows a specific hierarchy outlined in the rules.

The first part of the correct option specifies that you apply "effects from CDAs first." CDA refers to "characteristic-defining abilities," which are effects that define what a permanent is like outside of the game or specify attributes that are relevant in the game. Such effects must be resolved before others, as they can fundamentally alter a permanent's characteristics before any other effects are assessed.

Following the characteristic-defining abilities, all other effects must be applied in "timestamp order." This means that, when multiple effects are present, the most recently applied effects take precedence over earlier ones. This reflects the principle that newer changes can override previous ones, ensuring that players see the most current state of the game.

This systematic application ensures clarity and consistency in gameplay, allowing players and judges to understand how to interpret interactions correctly, which is vital for maintaining the integrity of the game.