Passive immunity can be conferred directly by

Options

A. vaccines
B. antitoxins
C. colostrum
D. both (b) and (c )

Explanation

**Step-by-Step Solution:**

1. **Understanding Passive Immunity**:
- Passive immunity is a type of immunity where an individual receives antibodies from another source rather than producing them through their own immune response. This can occur naturally or artificially.

2. **Identifying the Mechanism**:
- In passive immunity, the key feature is the direct transfer of antibodies. This can happen through various means, such as injections or maternal transfer.

3. **Evaluating the Options**:
- **Option A: Vaccine**: Vaccines introduce antigens to stimulate the immune system to produce its own antibodies, which is active immunity. Therefore, this option does not confer passive immunity.

- **Option B: Antitoxin**: Antitoxins are preparations that contain antibodies against specific toxins. When injected into an individual, they provide immediate immunity without the individual having to produce their own antibodies. This is a form of passive immunity.

- **Option C: Colostrum**: Colostrum is the first form of milk produced by mammals after giving birth. It is rich in antibodies (especially IgA) and provides these ready-made antibodies to the newborn, thus conferring passive immunity.

- **Option D: Both B and C**: Since both antitoxins and colostrum provide passive immunity, this option correctly identifies both sources.

4. **Conclusion**:
- The correct answer to the question is **Option D**, which states that passive immunity can be conferred directly by both antitoxin and colostrum.