Final answer:
The Officer in Charge is typically responsible for updating a toxic substance inventory list in an organizational structure, making option B the correct answer to the question.
Step-by-step explanation:
The correct answer to the question "The house_____________ shall ensure this list (toxic substance inventory list) is updated at least once a year" is B. Officer in Charge. In many organizational structures, the Officer in Charge is responsible for maintaining up-to-date records and ensuring that procedures such as the updating of a toxic substance inventory list are carried out as required. Although titles and specific duties can vary by organization, it is commonly the Officer in Charge who has the operational responsibility for tasks like inventory management.