From the same passage about snorkelling, answer the factual question “When would there be a risk of the tube falling off while observing the underwater world”.

Introduction / Context:
This question again checks close reading of the snorkelling passage. The writer describes how snorkelers must resist opening their mouths wide in amazement at the beauty of the underwater world, because doing so would disturb the tube used for breathing. The task is to identify the exact situation in which the tube might fall off. These questions strengthen the habit of focusing on small but important details in descriptive texts.

Given Data / Assumptions:
Key parts of the passage include:

• The writer and other snorkelers use a breathing tube connected to their masks.
• The underwater world is described as very beautiful and colourful.
• The writer notes that snorkelers struggled to resist opening their mouths wide in amazement.
• The passage explicitly states that if they opened their mouths wide, the tube would fall off.

Concept / Approach:
The breathing tube in snorkelling is held in place by the mouth. If the mouth shape changes too much, especially if it opens wide, the tube can loosen or come out. The passage directly connects the risk of the tube falling off with opening the mouth wide in amazement. None of the other conditions listed in the options are mentioned in the text. Therefore, the correct choice is the one that refers to opening the mouth wide, not to fogging, darkness, or nose breathing alone.

Step-by-Step Solution:
Step 1: Recall the sentence that explains the risk: snorkelers struggled to resist opening their mouths wide in amazement; the tube would fall off. Step 2: Identify the cause and effect in that line. Cause: mouth opened wide in amazement. Effect: tube would fall off. Step 3: Look at option d, when the mouth was opened wide in amazement. This matches the passage exactly. Step 4: Option a refers to mask fogging, which is controlled by breathing pattern, not by the tube position. Step 5: Option b mentions breathing through the nose, which is related to fogging, not directly to the tube falling off. Step 6: Option c talks about it becoming dark, which is not mentioned in connection to the tube at all. Step 7: Conclude that option d must be the correct answer.

Verification / Alternative check:
To verify, mentally replay the final lines of the passage. The writer emphasises the emotional reaction of snorkelers to the underwater beauty and links this reaction to a physical risk involving the tube. Since the tube is held by the mouth, opening the mouth widely would naturally disturb it. None of the other situations listed in the options are presented in the passage as causing the tube to fall off. This confirms option d as correct.

Why Other Options Are Wrong:
Option a is wrong because fogging affects visibility through the mask, not the stability of the tube. Option b is incorrect because breathing through the nose may fog the mask but does not directly cause the tube to fall off. Option c is wrong since darkness has no mechanical connection to the tube position. These options may look related to underwater conditions in general but do not match the specific cause given in the text.

Common Pitfalls:
Some students may assume that any difficulty mentioned earlier in the passage, such as mask fogging, must be the answer to later questions. Others may choose an option that seems physically possible but not stated in the text. To avoid such pitfalls, always distinguish between what the passage actually says and what might simply seem logical. Exam questions normally require the answer that is directly supported by the passage.

Final Answer:
There would be a risk of the tube falling off when the mouth was opened wide in amazement, as described in the passage.