Which of the following radiation sources is NOT suitable for food products?

Correct option is C

Option (c): Correct
• Selenium-75 is not approved or used for food irradiation because its gamma energy is insufficient and unstable for industrial food treatment.
Option (a): Incorrect
• Caesium-137 is approved and used for food irradiation.
Option (b): Incorrect
• Cobalt-60 is the most widely used gamma source for food processing.
Option (d): Incorrect
• X-rays (generated from 5 MeV sources) are permitted for food irradiation.
Hence Selenium-75 is the unsuitable source.