A) Python identifiers must begin with a capital or lower case letter (A to Z and a to z) or underscore ( _ ). The initial character may be followed by zero or more letters, underscores, or digits, in any combination. Write a regular expression for such identifiers (10 points)

B)Write a regular expression (RE) for Social Security Number (SSN). Your rule will match a hyphen-separated SSN in the format NNN-NN-NNNN, but the first digit cannot be a zero. Example: 111-22-9912 (valid) 010-56-0987 (invalid) (10 points)

C) Write at least four different numbers (must of different look) generated by the following regular expression: [0-9]+((E|e)(\+|\-)?[0-9]+)? (10 points)