Final answer:
Elsa's act of reading to her sister reflects the tertiary sector of industry, which provides services like child care and informal education.
Step-by-step explanation:
The component of industry that Elsa's ability to read picture books to her sister Anna most reflects is the tertiary sector. This sector is responsible for providing services such as child care, healthcare, and money management. Since reading to a younger sibling is an informal educational service, it aligns with services typically found in the tertiary sector. Although not a professional or commercial service, it embodies the essence of the sector through the act of sharing knowledge and caregiving.