Final answer:
The skull & crossbones symbol on a label indicates that a substance is toxic and can cover several hazards, including toxic vapors, deadly oral ingestion, and injury from skin contact, thus the answer is D. All of the above.
Step-by-step explanation:
A skull & crossbones symbol on a label is commonly used to indicate that a substance is toxic or harmful. This symbol doesn't specify the exact nature of the hazard but generally communicates that the chemical can pose a serious health risk if not handled properly.
The hazards could include being highly toxic through inhalation of vapors, causing death if taken orally, or causing injury if the substance spills on the skin. Therefore, the correct answer would be D. All of the above.