Find the number molecules in which $3c-2e^{-}$ bonds are present 

${\mathrm{AlCl}}_8,{\mathrm{BH}}_3,{\mathrm{BeH}}_2,\mathrm{Be}\left({\mathrm{Me}}_2,{\mathrm{Si}}_2{\mathrm{H}}_6,{\mathrm{C}}_2{\mathrm{H}}_6\right.$

A three-center two-electron (3c–2e) bond is the type of electron-deficient chemical bond in which three atoms share two electrons.

There is no molecule in which $3c-2e^{-}$ bonds are present  Thus, correct answer is zero.