Question

before excavation work begins, employers must:
evaluate the soil conditions
test oxygen levels
determine safe entry and exit points
all of the above

Explanation:

For excavation work, evaluating soil conditions (to check for stability, type, etc.), testing oxygen levels (to ensure a safe atmospheric environment for workers), and determining safe entry/exit points (for worker safety during emergencies or routine access) are all essential pre - excavation tasks. So all of these actions are required.

Answer:

All of the above