Which one of the following is the correct statement?

• A

  Boric acid is a protonic acid
• B

  Beryllium exhibits coordination number of six
• Correct answer
  C

  Chlorides of both beryllium and aluminium have bridged chloride structures in solid phase
• D

  $\mathrm{B}_2 \mathrm{H}_6 .2 \mathrm{NH}_3$ is known as 'inorganic benzene'

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