A.I. Explanation:

Option 1: "in difficulty"

Explanation: This option does not align with the context of the text. The phrase 'in difficulty' suggests a general state of struggle or hardship, which is not what the author is conveying. The text specifically mentions the need for proper training to avoid putting oneself 'in danger,' making this option irrelevant.

Option 2: "in a problem"

Explanation: While 'in a problem' implies facing an issue, it lacks the specific connotation of risk that 'in danger' provides. The text emphasizes the potential hazards of scuba diving without proper training, making this option too vague and not directly supported by the text.

Option 3: "in danger"

Explanation: This option is correct as it directly reflects the author's warning about the risks associated with scuba diving without adequate training. The phrase 'in danger' is explicitly mentioned in the text, highlighting the importance of proper knowledge to ensure safety while diving.

Option 4: "in addition"

Explanation: The phrase 'in addition' suggests adding information rather than addressing a risk or consequence. This option does not fit the context of the sentence, which focuses on the dangers of scuba diving without training, making it irrelevant to the main idea presented in the text.