26.
Your Answer is
Correct Answer is H
Explanation
Judge the predicate verb as had performed according to the meaning of the clause and the following time word (for years). Item H is correct in past perfect tense.
Item J: did performed is the wrong form of verb expression.
Item F/G: The underlined part guides the attributive clause to modify the instructor, and the clause lacks a subject. You must choose the nominative who, and you cannot choose the accusative who.