Explanation:

This is to be noted in the above question that these are also the natural sources of radioactive pollution. Besides the 4 mentioned above, radium-224 and uranium-238 are also sources of radioactive pollution.

Radioactive pollution in aquatic organisms can also be seen as:
1.    Oyster accumulate Zn65.
2.    Fishes accumulate Fe55
3.    Marine animals Sr90
 All of the above are correct.
The sources of radioactive pollution include:
Artificial Sources of Radioactive pollution
• Accidents in nuclear power plants and nuclear waste.
• Nuclear weapon testing and explosion (Nuclear fallout). The fall Out contains radioactive substances such as strontium-90, cesium-137, iodine-131, etc.
• Uranium mining and mining of other radioactive material like thorium Uranium contamination is well observed in India.
• Radiation therapy and direct exposures to radiation for diagnostic purposes (e.g. X-rays), chemotherapy etc.
• The slow nuclear radiations can emanate from a variety of sources viz. nuclear reactors, laboratories, hospitals, and direct exposures to X-rays etc.

Natural Sources
• They include cosmic rays from space and terrestrial radiations from radio-nuclides present in earth’s crust such as radium-224, uranium-238, thorium-232, potassium-40, carbon-14, etc.
• Some species of animals and plants preferentially accumulate specific radioactive, materials. For example, oysters deposit 65Zn, fish accumulate 55Fe, marine animals selectively deposit 90Sr.