To answer this question, we need to understand the concept of identifiers in programming.
An identifier is a name given to a variable, function, or any other user-defined item in a program. It is used to uniquely identify these items within the program.
Let's go through each option to understand why it is correct or incorrect:
Option A) An identifier can include letters and the first character can be a letter.
This option is correct. In most programming languages, an identifier can include letters (both uppercase and lowercase) and the first character can be a letter.
Option B) An identifier can include digits, but the first character cannot be a digit.
This option is correct. In most programming languages, an identifier can include digits, but the first character cannot be a digit. It must be a letter or an underscore.
Option C) An identifier's length can exceed the length of the current line.
This option is incorrect. The length of an identifier is typically limited by the programming language or the specific implementation. It cannot exceed the length of the current line.
Option D) The symbol for PI (3.14159...) is a valid identifier.
This option is correct. In most programming languages, the symbol for PI (π) can be used as part of an identifier. However, it is worth noting that the specific rules for identifiers may vary between programming languages.
Based on the explanations above, the incorrect statement about an identifier is Option C. The length of an identifier cannot exceed the length of the current line.
Therefore, the correct answer is C) An identifier's length can exceed the length of the current line.