The steady and sharp fall in coal prices has knocked down shares of big mining companies like BHP Billiton (NYSE: BBL - news ) , Glencore (Xetra: A1JAGV - news ) and Rio Tinto (LSE: RIO.L - news ) , and it has seen many financers exit the sector.
What is the relationship between 'Glencore' and 'mining' in the context of the input sentence.
Options: chairperson, product/material produced, industry, stock exchange