Exam 300-820 topic 1 question 12 discussion

\d: This is a special sequence in regex that matches any digit (equivalent to [0-9]). {3}: This is a quantifier that specifies exactly how many times the preceding element should be repeated. In this case, it means that exactly three digits should be matched. (\d{3}): The parentheses around \d{3} create a capture group. This means that the matched sequence of three digits is stored as a group, which can be referenced later in the regex or in the code that uses the regex. So, the entire regex (\d{3})(\d{3})(\d{3})(\d{3}) matches a string that consists of four groups of exactly three digits each. C&E contain 4 groups of 3 digits.

The third use of backslash is for specifying generic character types. The following are always recognized: \d any decimal digit \D any character that is not a decimal digit \s any whitespace character \S any character that is not a whitespace character \w any "word" character \W any "non-word" character \d{8} matches exactly 8 digits. An opening curly bracket that appears in a position where a quantifier is not allowed, or one that does not match the syntax of a quantifier, is taken as a literal character.

CE are correct