Question 1112711
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Some of your classmates might have more than one email address.  If so, then the relation between your classmates and their email addresses is not a function.<br>
They can also have more than one phone number, so the relation between them and their phone numbers might not be a function.<br>
But nobody should have more than one social security number, so the relation between your classmates and their social security numbers should be a function.  If it is not, then there is some fraud going on....