Fill in the blank with a suitable adverb : “ ________ , he thinks too…

The correct answer is Option (2) - unfortunately

 

• "Unfortunately" fits the sentence as it conveys regret or disapproval about the fact that "he thinks too high of himself."
• "Slyly" implies deceitfulness, which does not suit the context.
• "Recently" refers to time but does not align well with the evaluative tone of the sentence.
• "Credibly" means believably or convincingly, which is irrelevant here.