**Core Concept**
Tetanus neonatorum is a life-threatening infection that occurs in newborns due to Clostridium tetani spores contaminating the umbilical stump. The prevention of tetanus neonatorum involves ensuring that the umbilical stump is kept clean and dry, and that the birth attendant is properly immunized against tetanus.

**Why the Correct Answer is Right**
The best preventive measure against tetanus neonatorum is to ensure that the birth attendant is properly immunized against tetanus. This is because the birth attendant is at risk of introducing tetanus spores into the environment, which can then contaminate the umbilical stump. By immunizing the birth attendant, the risk of tetanus spores being introduced is significantly reduced. This is in accordance with the World Health Organization's recommendations for preventing tetanus neonatorum.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not specified, but if it refers to tetanus toxoid vaccination of the newborn, it is not the best preventive measure. While tetanus toxoid vaccination is an important part of preventing tetanus, it is most effective when administered in a series of injections, starting before birth.
* **Option B:** This option is not specified, but if it refers to keeping the umbilical stump moist, it is actually a wrong approach. Keeping the umbilical stump moist can actually increase the risk of tetanus infection, as it creates an environment that is conducive to the growth of C. tetani spores.
* **Option C:** This option is not specified, but if it refers to the use of antibiotics to prevent tetanus, it is not the best approach. While antibiotics may be used to treat tetanus infection, they are not effective in preventing it.

**Clinical Pearl / High-Yield Fact**
A mnemonic to remember the key components of preventing tetanus neonatorum is "CLEAN": Clean the umbilical stump, Keep it dry, Ensure the birth attendant is immunized, Avoid introducing tetanus spores into the environment.

**Correct Answer:** D.