In the reactions $\mathrm{I}$ and $\mathrm{II}$ the covalencies of $\mathrm{Be}$ and $\mathrm{Al}$ in $\mathrm{X}$ and $\mathrm{Y}$ are respectively I $\mathrm{Be}(\mathrm{OH})_2+\underset{\text { (excess) }}{\mathrm{NaOH}} \rightarrow \mathrm{X}$ (excess) II $\mathrm{Al}(\mathrm{OH})_3+\underset{\text { (excess) }}{\mathrm{NaOH}} \rightarrow \mathrm{Y}$

• A

  4,6
• Correct answer
  B

  4,4
• C

  6,4
• D

  3,6

Solution

The covalencies of $\mathrm{Be}$ and $\mathrm{Al}$ in $\mathrm{X}$ and $\mathrm{Y}$ respectively are 4,4 .

Hence, the correct answer is option: 'B'.