Can 'Who' Fill the Blank: 'He is not ___________ he was a few years ago'?

'Who' cannot be used to fill the blank in the sentence 'He is not ___________ he was a few years ago'. This is because 'who' is a pronoun used to refer to a person. The blank in the sentence requires a word that describes a state or condition, not a person. For example, you could use words like 'as,' 'what,' or 'how' to complete the sentence, depending on the intended meaning.