Approximately % of the world's sewage is discharged untreated into the world's rivers and oceans.

Out of the following given choices;

15

7

24

95

The answer is 95%. The biggest contributors of this percentage are developing countries that do not have proper waste disposal  mechanisms such as well structured sewer systems.  It is estimated that 70% of industrial wastes in developing countries are disposed off untreated into waters where they end up in oceans through rain wash.

this would be a math