Analyze the relationship between 'Citadel LLC' and 'hedge fund' within the context of the input sentence.
Options: operator, chairperson, industry, director/manager

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.
industry