    Senteri¢e I: Searches for-survivors from several  previous “shipwrecks have often had -to be  abandoned: for’ similar .reasons ; leaving the  vessels « and most of. their’ passengers  unaccounted for :    Sentence 2:'in several previous shipwrecks , the  search for survivors had to be abaridoned for  similar reasons ; leaving the vessels and most of  their passengers unaccounted for .    