The word "tangent" comes from the Latin root "tangere," which means "to touch." In mathematics, a tangent refers to a line that touches a curve at a single point without crossing it. In a more general sense, "tangent" can refer to something that touches upon a topic or idea but does not delve into it deeply.
In the context of your sentence about formal gardens, the most appropriate definition would be "B. traveling." This is because the tangent gravel path you're describing would be a path that touches or runs alongside the circular flower beds, allowing for movement around the garden while indicating a direct connection to each flower bed.
However, please note that "tangent" is not commonly used to describe paths in gardens and may instead be interpreted more literally in mathematical or conceptual discussions.