Despite a growing population, in 1998 the United States used 38 billion fewer gallons of water a day when comparing it to the period of all-time highest consumption almost 20 years earlier.

A.day when comparing it to the period of all-time highest consumption almost 20 years earlier
B.day than it did during the period of all-time highest consumption almost 20 years earlier
C.day than were used almost 20 years earlier, which had been the all-time high consumption
D.day, compared to almost 20 years earlier, that having been the all-time high consumption
E.day, which is in comparison to the period of all-time highest consumption almost 20 years earlier

OA:B

POE!!! please help with Comparison error