Pick out correct statements regarding orystalline form of boran

Options

A. All allotropic forms of boran contais is icosahedral units with boran atoms at all 12 corners.
B. In `B_(12)` units each boran atoms is bonded to five boran atoms as a distance of `1.77 Å`
C. `alpha` - rhombohedral form of boran consists of layers of icosahedra linked with in each layer by three centre B-B bonds and between layers B-B bonds
D. `beta` - rhombohedral form consists of `12B_(12)` icosahedra arranged icoshedral about central `B_(12)` unit `(B_(12)(B_(12))_(12))`

Answer

A, B, C, D

Explanation

Allotropy of boron contains icosahedral units and boran atoms at 12 carbons.
In `B_(12)` units each boran atom is bonded to 5 boron atoms `beta` rhombo hedral consists of 12 `B_(12)` icosahedral arrangement.