In the following passage some of the words have been deleted. Read the passage carefully and selected the correct answer for the given blank out of the four alternatives.
As an industrial solvent, pyridine is used in a (1) ____________ range of manufacturing processes. It is also a by-product of coking coal, a crucial (2) ____________ for steel production. The Tees area was home to both steel and chemical (3) ____________ and the discharge of contaminated effluent (4) ____________ the river and surrounding wetlands has been (5) ____________ practice, often with minimal or no treatment.