Utilize the input text as a context reference, choose the right relationship between iShares and BlackRock from the options. Options: product/material produced, manufacturer, distributed by, industry, position held, original broadcaster, owned by, founded by, distribution format, headquarters location, stock exchange, currency, parent organization, chief executive officer, director/manager, owner of, operator, member of, employer, chairperson, platform, subsidiary, legal form, publisher, developer, brand, business division, location of formation, creator.

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.”

Answer: operator