Utilize the input text as a context reference, choose the right relationship between Optus and SingTel 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.

The latest Optus results showed the willingness of parent company SingTel to invest in the business.

Answer: parent_organization