Final answer:
The brain network engaged while Selena daydreams is the default network, which is active during internal thought and reflection.
Step-by-step explanation:
While Selena weeds her garden and daydreams about what she will wear to her daughter's graduation ceremony, the brain network that is engaged is known as the default network. This network is associated with a state of mind where one is not focused on the outside world and the brain is wakefully resting, such as when daydreaming or engaging in internal thought. The default network allows us to reflect on our personal experiences, think about the future, and engage in mental simulations.