Like you guys I think D would be the most suited answer. However, the answer provided byu Vstudy is B.
So.. I started to wonder if there are some cases where the second "AS" could be omitted when using "AS GREAT OR GRATER...THAN"
It cannot be B. B has a redundancy. "at least" implies "as great as or greater than"
Former Senior Instructor, Manhattan GMAT and VeritasPrep
Vice President, Midtown NYC Investment Bank, Structured Finance IT
MFE, Haas School of Business, UC Berkeley, Class of 2005
MBA, Anderson School of Management, UCLA, Class of 1993