Which of the following statements is not correct?

Options

A. (a) Higher vertebrates can distinguish foreign organisms from self-cells.
B. (b) Fetus receives antibodies from its mother through placenta, is an example of active immunity.
C. (c) Cell-mediated immunity involves T-lymphocytes.
D. (d) Antibodies against cancer-specific antigens are used for detection of certain cancers.

Explanation

To determine which of the following statements is not correct, we will analyze each option provided in the question.

1. **Option A**: "Higher vertebrates can distinguish foreign organisms from self-cells."
- This statement is **true**. Higher vertebrates have a well-defined immune system that can differentiate between self (the body’s own cells) and non-self (foreign organisms, also known as antigens). This ability is crucial for the immune response.

2. **Option B**: "Peter's received antibody from its mother through placenta is an example of active immunity."
- This statement is **false**. The transfer of antibodies from mother to fetus through the placenta is an example of **passive immunity**, not active immunity. Passive immunity involves the transfer of pre-formed antibodies, while active immunity involves the body producing its own antibodies in response to an antigen.

3. **Option C**: "Cell-mediated immunity involves T-lymphocytes."
- This statement is **true**. Cell-mediated immunity primarily involves T-lymphocytes, which include T helper cells, T cytotoxic cells, and T suppressor cells. These cells play a crucial role in the immune response.

4. **Option D**: "Antibodies against cancer-specific antigens are used for detection of certain cancers."
- This statement is **true**. Antibodies can be developed to target specific antigens present on cancer cells, and these antibodies can be used for both detection and treatment of certain cancers.

After analyzing all the options, we find that **Option B** is the only incorrect statement.

**Final Answer**: Option B is not correct.

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