The Tree Room in the poem refers to a room that is built on a tree where squirrels play. The poem describes a magical room that is constructed within the branches of a tree, providing a safe and playful haven for squirrels.

The poet uses vivid imagery to depict the Tree Room as a whimsical and enchanting space. Let's explore the reasons why the correct answer is option 'B':

1. Imagery of a room: The poem describes the Tree Room as a specific area within the tree where squirrels can gather and play. This suggests that the room is a defined space rather than just a general area on the tree.

2. Location on a tree: The poem explicitly mentions that the Tree Room is built on a tree. This indicates that it is not a separate structure but rather a part of the tree itself, highlighting the interconnectedness of nature.

3. Playful inhabitants: The poem states that squirrels play in the Tree Room. Squirrels are known for their agile and playful nature, making them the perfect inhabitants of such a room.

4. Squirrel-centric activities: The poem further describes the squirrels in the Tree Room as engaged in various playful activities, such as swinging from branches, chasing each other, and leaping from tree to tree. These actions emphasize the energetic and lively atmosphere of the room.

5. Symbolic representation: The Tree Room can be seen as a metaphor for a sanctuary or a safe space for animals. It represents a natural environment where animals can engage in their natural behaviors without fear or disturbance.

In conclusion, the Tree Room in the poem refers to a room built on a tree where squirrels play. This concept adds a touch of magic and wonder to the poem, showcasing the beauty and harmony of nature.