I am confused by the following sentence written by a veteran teacher. According to grammar rules, if an interrogative sentence starts with interrogative “who”, its following-up relative pronoun should use “that,” not “who.” So, is the relative pronoun “who” in the following sentence as written grammatically correct?
Who was the boy with a conical hat who crawled through the ladder in this photo from 50 years ago?
"Who was the man who" -- 260,000,000 Google hits
"Who was the man that" -- 121,000,000 Google hits
The results of an Ngram are interesting. They suggest that there was a preference for "that" for most of the 19th century.
See results here: https://books.google.com/ngrams/grap...20that%3B%2Cc0
Pope of the Dictionary.com Forum