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.”
Take context from the input text and decide on the accurate relationship between 'iShares' and 'BlackRock' from the options provided.
Options: operator, legal form, headquarters location, original broadcaster