Which of the following, if any, are invalid names for a variable? A. bankAccountNumber B. first_Name C. doubleNumber D. operator E. All of the above are valid names for variables

The correct answer is D. operator.

A variable name can be any combination of letters, numbers, and underscores, but it cannot start with a number or underscore. It cannot also be a keyword, which is a word that has a special meaning in the programming language. In Python, the keywords are:

• and
• as
• assert
• break
• class
• continue
• def
• del
• elif
• else
• except
• finally
• for
• from
• global
• if
• import
• in
• is
• lambda
• not
• or
• pass
• print
• raise
• return
• try
• while
• with

The name “operator” is a keyword in Python, so it cannot be used as a variable name.

The names “bankAccountNumber”, “first_Name”, and “doubleNumber” are all valid variable names in Python.