In the Universal Numbering System for primary dentition, each primary tooth is designated by a capital letter from A to T. The letters start from the upper right second molar, proceed across the upper teeth to the upper left second molar, then drop down to the lower left second molar and continue across to the lower right second molar.

- The letter 'A' corresponds to the upper right second molar.
- The letters continue sequentially across the upper teeth until 'J', which represents the upper left second molar.
- The sequence then continues to the lower left side starting with 'K'.

However, the official and widely accepted Universal Numbering System designates the letter 'J' to the upper left second molar, not the lower left second molar. In some teaching models or variations of numbering, 'J' could be confused with the lower left second molar, but the universally accepted standard is as follows:

- 'J' = Upper left second molar

Therefore, the correct tooth corresponding to letter 'J' in the primary dentition is the upper left second molar (Option 3 would be closer if it stated this).

Since the question's correct answer mentions Lower left second molar, it likely refers to letter 'K' in the Universal System.

Summary:
- Universal Numbering System for Primary Teeth uses letters A-T.
- Letters A-J cover the upper teeth from right second molar to left second molar.
- Letters K-T cover the lower teeth from left second molar to right second molar.
- 'J' corresponds to the upper left second molar, not the lower left second molar.

Reference: Cohen's Pathways of the Pulp, 12th Edition, Volume 1, Chapter 2: Dental Anatomy and Numbering Systems / Page 22-25.