If an Industry Currently Has Herfindahl-Hirschman Index (HHI)of 900 and a Merger

If an industry currently has Herfindahl-Hirschman Index (HHI) of 900 and a merger would raise that to 950,then the Department of Justice would _____

A) challenge the merger because the index would become too large.
B) challenge the merger because the change in the index is too large.
C) not challenge the merger because the post-merger index would be less than 2,500.
D) not challenge the merger if it is a horizontal merger.
E) challenge the merger if it is a vertical merger.