Explain the structures of diborane and boric acid.

(N/A) Diborane $(B_2H_6)$ is an electron-deficient compound with only $12$ valence electrons. The two $B$ atoms and four terminal $H$ atoms lie in the same plane,while the two bridging $H$ atoms lie in a perpendicular plane (one above and one below). The terminal $B-H$ bonds are $2c-2e$ (two-center-two-electron) bonds,and the bridging $B-H-B$ bonds are $3c-2e$ (three-center-two-electron) bonds.
$(b)$ Boric acid $(H_3BO_3)$ has a layered structure. Each planar $BO_3^{3-}$ unit is linked to others through $H$ atoms. The $H$ atoms form covalent bonds with the oxygen atoms of the $BO_3$ unit and hydrogen bonds with the oxygen atoms of adjacent $BO_3$ units.