Key tools to be involved in recombinant DNA technolgy are
Restriction enzymes
Polymerase enzyme
Ligase enzymes
Vectors

Options

A. (A) only
B. (A) and (C ) only
C. (A) , (B) and (C )
D. (A),(B) ,(C ) and (D)

Answer

### Step-by-Step Solution:

1. **Understanding Recombinant DNA Technology**:
- Recombinant DNA technology involves combining DNA from different sources to create new genetic combinations. This technology is crucial for various applications, including gene cloning, gene therapy, and the production of genetically modified organisms (GMOs).

2. **Key Tools in Recombinant DNA Technology**:
- **Restriction Enzymes**: These enzymes cut DNA at specific sequences. They are essential for isolating the desired DNA fragment from the source DNA and for cutting the vector DNA to allow for the insertion of the foreign DNA.
- **Polymerase Enzymes**: These enzymes synthesize new DNA strands by adding nucleotides to a DNA template. They are crucial for amplifying the DNA fragments during the cloning process.
- **Ligase Enzymes**: DNA ligase is used to join the DNA fragments together. After the foreign DNA is inserted into the vector, ligase seals the nicks in the sugar-phosphate backbone, creating a stable recombinant DNA molecule.
- **Vectors**: Vectors are DNA molecules used to deliver the foreign DNA into a host cell. They can be plasmids, viruses, or artificial chromosomes, and they carry the foreign DNA into the host where it can be replicated and expressed.

3. **Conclusion**:
- All the mentioned tools (restriction enzymes, polymerase enzymes, ligase enzymes, and vectors) are integral to the process of recombinant DNA technology. They work together to isolate, amplify, and insert foreign DNA into host organisms, facilitating the expression of new traits.

4. **Final Answer**:
- The key tools involved in recombinant DNA technology are:
- A) Restriction enzymes
- B) Polymerase enzymes
- C) Ligase enzymes
- D) Vectors
- Therefore, the correct answer is **A, B, C, D**.