Identify the correct statement for B₂H₆ from those given below :

(A) In B₂H₆, all B-H bonds are equivalent.

(B) In B₂H₆, there are four 3-centre-2-electron bonds.

(C) B₂H₆ is a Lewis acid.

(D) B₂H₆ can be synthesized from both BF₃ and NaBH₄.

(E) B₂H₆ is a planar molecule.

Choose the most appropriate answer from the options given below :

The most stable trihalide of nitrogen is :

Which one of the following elemental forms is not present in the enamel of the teeth?