Correct statements among a to d regarding silicones are :

(a)   They are polymers with hydrophobic character.
(b)   They are biocompatible.
(c)   In general, they have high thermal stability and low dielectric strength.
(d)   Usually, they are resistant to oxidation and used as greases.

The one that is extensively used as a piezoelectric material is :

Among the oxides of nitrogen : N₂O₃, N₂O₄ and N₂O₅; the molecule(s) having nitrogen-nitrogen bond is / are :

A group 13 element 'X' reacts with chlorine gas to produce a compound XCl₃. XCl₃ is electron deficient and easily reacts with NH₃ to form Cl₃X $$ \leftarrow $$ NH₃ adduct ; however, XCl₃ does not dimerize X is :