MOSCOW (Reuters) -International energy major BP has opted to leave Russia after Western countries imposed severe sanctions on its companies and individuals following Moscow’s military attack on Ukraine. BP, the biggest foreign investor in Russia, said it was abandoning its stake in state oil company Rosneft at a cost of up to $25 billion, shrinking its oil and gas reserves in half. Shell followed suit, saying it would divest of its exposure as well. Following are some facts about exposure of Western oil and gas companies to Russia, which calls its actions in Ukraine a “special operation”: BP T…