A displacement mechanism which relocates {HEAD ~ acceptable pieces} to avoid {TAIL ~ excessive trim} is labeled as B 
to avoid
A displacement mechanism which relocates { HEAD ~ acceptable pieces } to avoid { TAIL ~ excessive trim } is labeled as B
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH