The correct answer is C because the email must be normalized by removing only the subaddressing portion between the plus sign and the @, while preserving the domain. JSON_VALUE is the correct function to extract the scalar email value from the JSON document. Microsoft states that JSON_VALUE is used to extract a scalar value from JSON text.

Then REGEXP_REPLACE should remove the pattern \+.*@ and replace it with a single @. For example:

user1+promo@contoso.com → user1@contoso.com

Microsoft documents that REGEXP_REPLACE returns the source string with text matching the regular expression replaced by the replacement string, and that an empty or custom replacement string can be used to reshape the result.

Why the other options are wrong:

A removes everything from + to the end of the string, which would leave user1 and lose @contoso.com.

B tries to extract a string that already excludes +..., but it does not reliably reconstruct the normalized address in this pattern.

D also removes everything after +, including the domain, which is incorrect.

So the normalized-email expression is:

REGEXP_REPLACE(JSON_VALUE(Payload, ' $.customer_email ' ), ' \+.*@ ' , ' @ ' )