The major product obtained on the interaction of phenol with sodium hydroxide and carbon dioxide is salicylic acid. This reaction is known as the Kolbe-Schmitt reaction.

**Kolbe-Schmitt Reaction:**
The Kolbe-Schmitt reaction involves the reaction of phenol with sodium hydroxide and carbon dioxide to produce salicylic acid. The reaction proceeds through a series of steps as follows:

1. First, phenol (C6H5OH) reacts with sodium hydroxide (NaOH) to form sodium phenoxide (C6H5ONa) and water (H2O). This step is known as the phenolate ion formation:

C6H5OH + NaOH → C6H5ONa + H2O

2. Next, carbon dioxide (CO2) is introduced to the reaction mixture. The carbon dioxide reacts with the sodium phenoxide to form sodium salicylate (C6H4(OH)COONa):

C6H5ONa + CO2 → C6H4(OH)COONa

3. Finally, the sodium salicylate is acidified to convert it into salicylic acid (C6H4(OH)COOH). This is achieved by adding an acid, such as hydrochloric acid (HCl), to the reaction mixture:

C6H4(OH)COONa + HCl → C6H4(OH)COOH + NaCl

**Explanation:**
The major product obtained in this reaction is salicylic acid. This is because the reaction conditions favor the formation of salicylic acid over other possible products.

Salicylaldehyde (option a) is not obtained as a major product because the reaction conditions do not favor the oxidation of phenol to salicylaldehyde.

Aspirin (option b) is not obtained as a major product because the reaction conditions do not involve the esterification of salicylic acid.

Salol (option d) is not obtained as a major product because the reaction conditions do not involve the condensation of phenol with salicylic acid.

Therefore, the correct answer is option c, salicylic acid.