Explanation:

- Alkanes were originally given the name “paraffin.”

- The name comes from Latin, meaning "lacking affinity."

- This term reflects their chemical inertness.

- Thus, the correct answer is Option 4: Alkanes.

- Aldehydes are a class of compounds with a carbonyl group bonded to a hydrogen atom.

- They were not referred to as paraffin.

- Alcohols contain hydroxyl groups and have varied chemical reactivity.

- They were never labeled paraffin.

- Acids are known for their sour taste and reactive properties.

- They were not called paraffin either.