Explanation:

- Reduction: This refers to the process of gaining electrons, not losing them.

- Option 2: Oxidation: This is the correct answer. Oxidation is specifically the process where a substance loses electrons, often in reactions involving oxygen.

- Both oxidation and reduction: A redox reaction involves both processes occurring simultaneously but does not specifically denote losing electrons.

- Radiation: This involves the emission of energy or particles and is not related to the electron transfer process.