Insert appropriate words in the blank. Oil fitering equipment shall be such as will ensure that any oily mixture discharged into the sea after passing through the system has an oil content not exceeding () parts per million 5 10 15 20

15

The question is about the oil content limit for discharging oily mixtures into the sea after passing through oil filtering equipment. The correct answer is 15 parts per million, which is a common standard for such regulations. This ensures that the oil content in the discharged mixture is within the permissible limit, thereby preventing environmental pollution.