Arg-1 : the use of 900 toll numbers has been expanding rapidly in recent years Arg-2 : for a while, high-cost pornography lines and services that tempt children to dial (and redial) movie or music information earned the service a somewhat sleazy image (Comparison -wsj 2100) To identify the "Comparison" relation between the two arguments Arg-1 and Arg-2, the most crucial clues mainly lie in some content, like "expanding rapidly" in Arg-1 and "earned the service a somewhat sleazy image" in Arg-2, since there exists a contrast between the semantic meanings of these two text spans.
it is difficult to obtain sufficient information for pinpointing these words through scanning the argument pair left to right in one pass.