**Core Concept**
Glutaraldehyde is a disinfectant and fixative used in various medical and dental applications, including primary tooth pulpotomy. It has antimicrobial properties and helps in preserving the tooth structure. The concentration of glutaraldehyde used in dental procedures is critical to ensure its effectiveness while minimizing toxicity.

**Why the Correct Answer is Right**
The correct concentration of glutaraldehyde used in primary tooth pulpotomy is 2.00%. This concentration is effective in disinfecting the pulp tissue and preserving the tooth structure. The use of glutaraldehyde in dentistry is based on its ability to cross-link proteins, thereby inactivating enzymes and preventing microbial growth. In primary tooth pulpotomy, a concentration of 2.00% glutaraldehyde is often used to disinfect the pulp tissue and promote healing.

**Why Each Wrong Option is Incorrect**
**Option A:** 4.00% glutaraldehyde is too concentrated and can be toxic to the pulp tissue, leading to necrosis and tissue damage. High concentrations of glutaraldehyde can also cause irritation to the surrounding tissues.

**Option B:** 3.00% glutaraldehyde is not a commonly used concentration in primary tooth pulpotomy. The effectiveness of glutaraldehyde decreases with decreasing concentrations, making 3.00% less effective in disinfecting the pulp tissue.

**Option C:** 1.50% glutaraldehyde is too low in concentration to be effective in primary tooth pulpotomy. It may not provide sufficient disinfection of the pulp tissue, leading to persistent infection and tissue damage.

**Clinical Pearl / High-Yield Fact**
Glutaraldehyde toxicity can be minimized by using the correct concentration, avoiding prolonged exposure, and wearing protective gloves and eyewear. It is essential to follow proper protocols when using glutaraldehyde in dental procedures to ensure patient safety.

**✓ Correct Answer: D. 2.00% 2.00% glutaraldehyde is the correct concentration used in primary tooth pulpotomy.**