In the PCR technique, the heat resistant polymerase used is :

Options

A. primer
B. Taq polymerase
C. ethidium bromide
D. alkaline phosphatase

Answer

### Step-by-Step Solution:

1. **Understanding PCR Technique**:
- PCR stands for Polymerase Chain Reaction, which is a method used in molecular biology to amplify specific DNA sequences. It allows for the generation of millions of copies of a particular DNA segment in a short period.

2. **Identifying Key Components of PCR**:
- The PCR process involves several key components, including primers, nucleotides, a DNA template, and a DNA polymerase enzyme.

3. **Role of Polymerase in PCR**:
- The polymerase enzyme is crucial in PCR as it synthesizes new DNA strands by adding nucleotides to the growing DNA chain.

4. **Heat Resistance of Polymerase**:
- During PCR, the reaction mixture is subjected to high temperatures (around 95°C) to denature the DNA. Therefore, the polymerase used must be heat-resistant to withstand these high temperatures without denaturing.

5. **Identifying the Correct Polymerase**:
- The most commonly used heat-resistant polymerase in PCR is Taq polymerase, which is derived from the thermophilic bacterium Thermus aquaticus. This enzyme remains active at high temperatures, making it ideal for PCR.

6. **Evaluating the Options**:
- **Primer**: These are short sequences of nucleotides that initiate DNA synthesis but are not polymerases.
- **Stacked Polymerase**: This term does not refer to a known enzyme used in PCR.
- **Ethidium Bromide**: This is an intercalating agent used for visualizing DNA but is not involved in the amplification process.
- **Alkaline Phosphatase**: This enzyme removes phosphate groups and is not used in PCR.

7. **Conclusion**:
- Based on the above analysis, the correct answer is Taq polymerase, as it is the heat-resistant polymerase used in the PCR technique.

### Final Answer:
The heat-resistant polymerase used in the PCR technique is **Taq polymerase**.