Which is a normalization step?

What does the regex \d+ match?

In a certain programming language, the regular expression /\b99\b/ matches “99” and “99a”  but not “299”, “$99” and “ _99”. From the  information presented, what is included in the set of characters that form a word for that programming language ?

We intend to write a regular expression to match the string “The” however our regular expression is also matching strings like “other” and “them” because they contain the set of characters “the” in them. We fixed this by building an appropriate regular expression. Now our regular expression matches only “The”. Which of the following happened as a result :

Which regex pattern would most accurately match a standard email address (e.g., "user@example.com") with least error among the given options. Assume that underscores are not present in the email?