Which Surah mentions Zulqarnain ?

A. A’ssuff
B. Alkahaf
C. Al Baqarah
D. Al Mujadala

A very important MCQ which is multiple times repeated in PPSC Written Exams in the past. 

This question is asked in the Past Paper of “JUNIOR CLERK (BPS 11) IN PUNJAB POLICE DEPARTMENT (2017) ” as a 

• In which Surah of Quran, name of Zulqarnain is mentioned?

in Past Paper of “ASSISTANT PPSC (BPS – 16) 2016 ” and “JUNIOR PATROL OFFICER (BS-09) in Lahore Ring Road Authority (Communication and Works Department) – 2017” as a

• In which Surah of the Holy Quran is there a mention of Zulqarnain?