Hydrogen bonds form between the molecules of the hypothetical compound AH and do not form between BH molecules because

Answer 1

Since hydrogen bonding requires both a hydrogen as part of the molecule and available lone pairs of electrons to associate with the hydrogen, the reason here that AH might be able to for hydrogen bonds while BH molecules cannot is because BH molecules lack lone electron pairs for the hydrogen bonding, while AH does have lone electron pairs for hydrogen bonding.