On Monday, it froze a trading account linked to Citadel Securities, a unit of the U.S. group that also owns hedge fund Citadel LLC - the first time in the crackdown that a foreign firm confirmed one of its Chinese accounts had been suspended.
In the context of the input sentence, determine the relationship between 'Citadel LLC' and 'hedge fund'.
Options: chairperson, industry, operator, director/manager