The answer is C. Social security number
Step-by-step explanation:
Factors such as weight or blood pressure are not unique to individuals, indeed, many people can have the same weight or blood pressure. Due to this, this information cannot be used to steal someone's identity or pretend to be that person.
This does not occur with the social security number because each social security number identifies a particular individual. As a result, this information might be used by identity thieves because they can use the social security number of an individual and pretend they are this individual, which can be used to access services and benefits.