Please answer the following question: Extract the answer to the question from the following context. Question: What is the highest ranking listed? Context: Oklahoma is the nation's third-largest producer of natural gas, fifth-largest producer of crude oil, and has the second-greatest number of active drilling rigs, and ranks fifth in crude oil reserves. While the state ranked eighth for installed wind energy capacity in 2011, it is at the bottom of states in usage of renewable energy, with 94 percent of its electricity being generated by non-renewable sources in 2009, including 25 percent from coal and 46 percent from natural gas. Oklahoma has no nuclear power. Ranking 13th for total energy consumption per capita in 2009, Oklahoma's energy costs were 8th lowest in the nation.
A:
second-greatest number of active drilling rigs