The nine-\B_2-branch conjecture for minimal-ABC trees

Let a minimal-ABC tree be a tree minimizing the atom-bond connectivity index among trees of the relevant order, and let a $B_2$-branch denote the branch type used in the paper's classification of such trees.

Nine-$B_2$-branch conjecture. A minimal-ABC tree can contain at most nine $B_2$-branches.

The paper proves an upper bound of eleven $B_2$-branches and presents nine as the conjectured sharp bound, motivated by experimental results and known examples. The assertion is not resolved in the supplied text.