## Core Concept
Active immunity involves the production of antibodies by the individual's immune system in response to direct exposure to an antigen, either through infection or immunization. This type of immunity provides long-term protection against future infections. The question tests the understanding of how active immunity is acquired.

## Why the Correct Answer is Right
Active immunity is primarily acquired through two methods:
1. **Infection**: When an individual is infected with a pathogen, their immune system mounts a response to eliminate the infection. As part of this response, the immune system retains a "memory" of the pathogen, allowing for a quicker and more effective response upon future exposures.
2. **Immunization or Vaccination**: This involves the administration of a vaccine, which is a form of antigen. Vaccines stimulate the immune system to produce antibodies and immune cells that can recognize and attack specific pathogens, without causing the disease itself.

## Why Each Wrong Option is Incorrect
- **Option A:** This option is not provided, but typically, active immunity can be acquired through infection or vaccination, which are common methods.
- **Option B:** Similarly, without the specific content of Option B, we can infer that if it represents a method like vaccination or natural infection, it would be a correct method of acquiring active immunity.
- **Option C:** If Option C suggests a method such as immunization or natural infection, it would also be incorrect to say it does not provide active immunity.
- **Option D:** Given that the correct answer is , we can infer that likely represents a method through which active immunity is indeed acquired, such as through the use of vaccines or recovering from an infection.

## Why the Correct Answer is
Given that active immunity can be acquired through infection (natural or through live attenuated vaccines) and immunization (with inactivated or subunit vaccines), the correct answer likely refers to a method that does not result in active immunity. Typically, passive immunity, which involves the administration of pre-formed antibodies, does not lead to active immunity. This can be achieved through:
- Administration of immunoglobulins or antitoxins (which provide immediate, short-term protection).
- Mother-to-child transfer of antibodies during breastfeeding or across the placenta.

## Clinical Pearl / High-Yield Fact
A key point to remember is that **vaccination** provides active immunity by stimulating the body to produce its own antibodies and immune cells, offering long-term protection. In contrast, **immunoglobulins** provide passive immunity with immediate but short-term protection. This distinction is crucial for understanding how different types of immunity are acquired and their implications for disease prevention.

**Correct Answer: B. passive immunity**