Which of the following is this code an example of?
^(\+0?1\s)?\?\d{3}\)?[\s.-]\d{3}[\s.-]\d{4}$
an array
an object data structure
a null variable
a regular expression
^(\+0?1\s)?\?\d{3}\)?[\s.-]\d{3}[\s.-]\d{4}$
an array
an object data structure
a null variable
a regular expression