Multiple choice Which of the following is not an identifier? Area_of_circle Pi-value 4th semester Count2 Reveal answer Fill a bubble to check yourself C Correct answer Explanation In programming, identifiers cannot begin with a digit. '4th semester' starts with the number 4, making it invalid. Valid identifiers like 'Area_of_circle', 'Pi-value', and 'Count2' start with letters or underscores.