Rewrite each sentence below using a direct object pronoun. buscan al profesor de inglés.

The correct answer is:  "Lo buscan" . 

 {in which "lo" is the direct object pronoun referring to "him" ; that is, the:
"profesor de inglés" {English teacher/professor}.  Since "al profesor" is a Spanish "contraction" for "a + el profesor" ;  we know that this takes the mascular singular form for the direct object pronoun — which is:  "lo" .   We capitalize the first word, because in this case, the word, "Lo" , is at the beginning of the sentence.

The answer will be
Lo buscan