Biochemical Oxygen Demand (BOD) may not be a good index for pollution for water bodies receiving effluents from Petroleum industry, Sugar industry, Dairy industry, Domestic sewage.

BOD is increased by dumping off waste rich in phosphates and nitrogen compounds as these two favor algal growth causing algal bloom and death of other underwater plants due to lack of Sunlight. The presence of excess organic matter favors microbial growth and reduces available dissolved oxygen. Petroleum industry waste is rich in radium-based toxic substances that do not favor algal and plankton growth and no effect on BOD. Therefore, the correct answer is option A.