Compound X on reduction with `LiAlH_(4)` gives a hydride Y containing 21.72% hydrogen and other products. The compound Y reacts with air expolosively resulting in boron trioxide. What are X and Y respectively ?
A. `BCl_(3), B_(2)H_(6)`
B. `PCl_(3), B_(2)H_(6)`
C. `B_(2)H_(6), BCl_(3)`
D. `LiAlH_(4),PCl_(3)`