The correct answer is option 'C', which is "Restriction endonucleases".

Restriction endonucleases, also known as restriction enzymes, are enzymes that are capable of cutting DNA molecules at specific sequences. They are found in bacteria and are part of the bacterial defense system against foreign DNA, such as viruses. The discovery and study of restriction enzymes have revolutionized molecular biology and genetics.

Below is a detailed explanation of restriction endonucleases and their role in DNA cutting:

1. What are restriction endonucleases?
- Restriction endonucleases are enzymes that recognize specific DNA sequences, called recognition sites, and cut the DNA at or near these sites.
- They are named after the bacteria from which they were first isolated. For example, the enzyme EcoRI was isolated from Escherichia coli strain RY13.
- Restriction endonucleases are classified into different types based on their structure and mechanism of action. Common types include Type I, Type II, and Type III restriction enzymes.

2. Mechanism of action:
- Type II restriction endonucleases are the most commonly used enzymes in molecular biology research.
- They recognize specific palindromic DNA sequences, where the sequence on one strand is the reverse complement of the sequence on the other strand.
- After binding to the recognition site, the enzyme cuts the DNA at specific positions within or near the sequence, resulting in DNA fragments with sticky ends or blunt ends.

3. Types of DNA cuts:
- Restriction endonucleases can produce different types of DNA cuts, depending on the position and orientation of the recognition site.
- If the enzyme cuts both DNA strands at the same position, it produces blunt ends.
- If the cuts are staggered on the two DNA strands, it produces fragments with sticky ends. The sticky ends can easily form hydrogen bonds with complementary sequences and be joined together.

4. Applications of restriction endonucleases:
- Restriction endonucleases are widely used in molecular biology techniques, such as DNA cloning, gene expression analysis, and DNA sequencing.
- They are used to cut DNA at specific sites, allowing the insertion of foreign DNA into a plasmid or vector during DNA cloning.
- Restriction enzymes are also used in DNA fingerprinting, where they cut DNA at specific sites to create unique patterns that can be used for identification purposes.

In conclusion, restriction endonucleases are enzymes that cut DNA at specific sequences. They play a crucial role in molecular biology research and have various applications in DNA manipulation and analysis.