He is accustomed _________ drinking so much.
He is accustomed _________ drinking so much.
Explanation
The phrase accustomed ended with “To” and is followed by “ing” form of a verb.
Accustomed to something means کسی چیز کا عادی ہونا
He is accustomed to drinking so much means وہ بہت زیادہ پینے کا عادی ہے