Which country is the largest producer of Shale Gas?

A. Russia
B. USA
C. Saudi Arabia
D. Iran

Shale gas is natural gas that is found trapped within shale formations. Shale gas has become an increasingly important source of natural gas in the United States since the start of this century, and interest has spread to potential gas shales in the rest of the world.
North America leads the worldwide production of shale gas, with the US and Canada having significant levels. Beyond the US and Canada, shale gas is so far produced at a commercial scale only in Argentina and China.