At step 25, the ACS 1050 assesses risk level and presents {HEAD ~ challenge} for {TAIL ~ high risk transactions} 
At step 25 , the ACS 1050 assesses risk level and presents { HEAD ~ challenge } for { TAIL ~ high risk transactions }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL