Which of these is most likely to produce heavy metal waste? a. leather tannery b. medical center c. paper mill d. oil refinery

Option A, Leather tannery

Explanation:

In a leather industry, chromium is one of the heavy metals that are used in large amount.  

Along with tannery, Chromium is also used in electroplating, and metallurgical industries.  

The water coming out of these tannery has high content of chromium ion (Cr6+) generally ranging between 100–200 mg/L. This chromium rich water needs sufficient treatment before discharge or else it would cause bio magnification effect

Hence, option A is correct