Hazrat ___________ added 2nd Azan for Friday prayers.

A. Hazrat Abu Bakr (R.A)
B. Hazrat Umar (R.A)
C. Hazrat Usman (R.A)
D. Hazrat Ali (R.A)

According to Bukhari, Volume 2, Book 13: Friday Prayer
Volume 2, Book 13, Number 38 :

Narrated by As-Sa’ib bin Yazid I

‘Hazrat Uthman bin ‘Affan introduced the second Adhan on Fridays when the number of the people in the mosque increased. Previously the Adhan on Fridays used to be pronounced only after the Imam had taken his seat (on the pulpit).