What are the approximate $H-B-H$ bond angles in diborane $(B_2H_6)$?

Identify the correct statements from the following:
$(i)$ The atomic radius of $Al$ is lower than the atomic radius of $Ga$.
$(ii)$ Boron exists in many allotropic forms.
$(iii)$ The melting point of $Ga$ is lowest among the group $13$ elements.

Identify the correct statements from the following:
$(a)$ In orthoboric acid, boron is in planar geometry.
$(b)$ In $BCl_3 \cdot NH_3$, boron has tetrahedral geometry.
$(c)$ Aqueous solution of borax is acidic.

When a mixture of diborane and ammonia is heated,the final product is:

Which of the following compounds is electron-deficient?

Which of the following structures is similar to graphite?