Step 1: Understanding the number of stock exchanges. 
  
Stock exchanges are venues where securities such as stocks and bonds are bought and sold. In India, there were 23 stock exchanges in 2004, as per the regulations and structure at that time. 
Step 2: Analyzing the options. 
  
(A) 20: Incorrect. This is lower than the actual number of stock exchanges in India in 2004. 
  
(B) 21: Incorrect. While close, this number does not represent the correct count. 
  
(C) 23: Correct. India had 23 stock exchanges in 2004. 
  
(D) 24: Incorrect. This number is slightly higher than the actual count. 
Step 3: Conclusion. 
  
The correct answer is (C) 23, as India had 23 stock exchanges in 2004.