Fill in the blank: Mark Wiedman, global head of BlackRock Inc. BLK 2.51 % ’s iShares unit, defended how an iShares ETF performed during recent market turmoil, saying it only “had ____ where it didn’t function properly.”
What is the relationship between 'iShares' and 'BlackRock' in the context of the input sentence.
Options: legal form, operator, original broadcaster, headquarters location