{HEAD ~ A challenge question} can be presented to {TAIL ~ the cardholder}, and the cardholders response can be verified 
{ HEAD ~ A challenge question } can be presented to { TAIL ~ the cardholder } , and the cardholders response can be verified
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH