Which Event Was Initially Responsible for London Becoming the Leading

Which event was initially responsible for London becoming the leading center of eurocurrency trading?

A) Regulations that discouraged British banks from trading in the eurocurrency market.
B) Strengthening of the British pound against major European currencies in the 1960s.
C) Collapse of the Bretton Woods system.
D) Prohibition of British banks from lending British pounds to finance non-British trade.