The Manager of Callow Youth Clothing Was Entering an Order

The manager of Callow Youth Clothing was entering an order online from Sad Clown Pajamas.He entered all the items and quantities,completed the checkout and payment process,but the following error message popped up when he tried to exit the site: "Please enter your email address." This message is likely the result of a

A) customer relationship management software application.
B) validity check.
C) completeness test.
D) closed-loop verification.