**Core Concept**
Injectable tetanus toxoid is a type of vaccine that contains inactivated tetanus toxin, which is used to stimulate the body's immune response against tetanus infection. This vaccine works by inducing the production of antibodies against the tetanus toxin, thereby providing immunity against the disease.

**Why the Correct Answer is Right**
Tetanus toxoid is an example of a toxoid vaccine, which is a vaccine that contains a toxin or a toxin component that has been inactivated or modified to be non-toxic. The inactivated toxin stimulates the immune system to produce antibodies against the toxin, thereby providing immunity against the disease. In the case of tetanus toxoid, the inactivated toxin is mixed with a carrier protein, such as aluminum phosphate, to enhance its immunogenicity.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because tetanus toxoid is not an example of a live attenuated vaccine, which contains a weakened form of the pathogen.
**Option B:** This option is incorrect because tetanus toxoid is not an example of a subunit vaccine, which contains only a specific component of the pathogen, such as a protein or sugar.

**Clinical Pearl / High-Yield Fact**
Tetanus toxoid is typically administered in combination with diphtheria toxoid as part of the diphtheria, tetanus, and pertussis (DTP) vaccine, which is a common childhood vaccine. Booster shots of tetanus toxoid are recommended every 10 years to maintain immunity against tetanus.

**Correct Answer: C. Toxoid vaccine.**