Q.Boric acid is polymeric due to

1. Structure of boric acid. Boric acid, $\text{H}_3\text{BO}_3$ (or $\text{B(OH)}_3$), consists of planar, triangular units in which boron ($sp^2$ hybridised) is bonded to three –OH groups.
2. How these units link up. Each –OH group can act as both a hydrogen-bond donor and acceptor, so individual $\text{B(OH)}_3$ units link to their neighbours through hydrogen bonds, building up an extended two-dimensional sheet.
3. Why this is "polymeric." This hydrogen-bonded network of repeating \text{B(OH)}_3} units extending over a large sheet is what gives boric acid its layered, polymer-like solid structure — the layers themselves are then held together only by weaker van der Waals forces (giving the solid its softness/flakiness). …

Recall boric acid's solid-state structure: planar $sp^2$ B(OH)$_3$ units linked into 2-D sheets specifically via intermolecular hydrogen bonding between –OH groups, distinguishing this cause from its acidic/monobasic solution behaviour or its mol …

• Confusing the reason for boric acid's acidity in solution (its Lewis-acid behaviour) with the reason for its polymeric solid-state structure (hydrogen bonding) — these are two separate properties. …