The correct answer is (d). The 7th BRICS Summit of 2015 was held in Ufa, Russia.
Abaza is a town in the Republic of Adygea, Russia. It is located on the left bank of the Belaya River, 100 kilometers (62 mi) north of Maykop, the capital of Adygea. The town has a population of 45,000 people.
Balakovo is a city in Saratov Oblast, Russia. It is located on the Volga River, 100 kilometers (62 mi) north of Saratov. The city has a population of 117,000 people.
Kotovo is a town in Saratov Oblast, Russia. It is located on the Volga River, 120 kilometers (75 mi) north of Saratov. The town has a population of 15,000 people.
Ufa is the capital of Bashkortostan, Russia. It is located on the Belaya River, 1,400 kilometers (870 mi) east of Moscow. The city has a population of 1,116,000 people.