With Regard to the 2008 Discovery of Bernard Madoff's Ponzi

With regard to the 2008 discovery of Bernard Madoff's Ponzi scheme, which of the following is not true?

A) He preserved an element of secrecy by claiming his investment strategy to be a trade secret.
B) The scheme lasted over 20 years and cost his clients billions of dollars.
C) Obtaining investment funds from charities and nonprofits was an essential part of his strategy.
D) To keep multiple authorities and governments from examining his operation, he restricted the scheme to U.S. investors and U.S. business entities only.