Answer:
Correct answer is: C. Russia
Step-by-step explanation:
A is not correct answer as Mongols never reached western Europe during their conquest, not only during the reign of Genghis Khan, but in general.
B is not correct answer as Saudi Arabia was never part of Mongolian Empire.
C is correct because he managed to take part of todays Russia, after he defeated Kievan Russ troops.
D is not correct as Iraq was not conquered during his reign, but in 1258.