This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
Which of the following phrases best describes restriction enzymes? 
Select and explain. 
A. Site-specific endonucleases., B. Enzymes that regulate RNA., C. Nonspecific endonucleases., D. Topoisomerases.
A: Site-specific endonucleases.
Answer: A: Site-specific endonucleases. 
Explanation: Restriction enzymes are also known as restriction endonucleases. These enzymes cleave DNA at specific sites to release fragments of DNA for further analysis and characterization by complementary probes.