Anhydrous $AlCl_3$ is covalent; however,when it is dissolved in water,hydrated ionic species are formed. This transformation is owing to

• A
  the trivalent state of $Al$
• B
  the large hydration energy of $Al^{3+}$
• C
  the low hydration energy of $Al^{3+}$
• D
  the polar nature of water