Which of the following Python variable name is valid? A. first exam B. first-exam C. 1st_exam D. first_exam

Out of the following, the Python variable name that is valid is first_exam.

Explanation:

In Python, the set of rules applied for the validity of the variable names requires the variable name to be in a specified format.

The format is characterized by the use of underscore signs ('_') instead of using space or hyphens in between two words that make the variable name.

If the variable name is not in the specified format, the program may most probably exhibit error.