In the following sentence, a blank is given. Choose the correct word to fill in the blank. At night, the winding roads can make driving up the mountain a ______________ journey.

Introduction / Context:
This is a vocabulary in context question that asks the learner to choose the most appropriate adjective to describe a journey up a mountain on winding roads at night. The correct choice should reflect both the physical difficulty and the potential danger of the situation. The options include words that describe emotional states or unpleasant qualities, but only one of them captures the idea of danger and risk in travel conditions.

Given Data / Assumptions:

• The sentence speaks about "winding roads" and "driving up the mountain".
• The time is at night, which reduces visibility.
• We need an adjective that fits naturally before "journey".
• Options: "carefree", "beastly", "obnoxious", "treacherous".

Concept / Approach:
The word "treacherous" is often used to describe conditions that are dangerous and deceptive, such as treacherous roads, treacherous ice, or treacherous weather. It does not simply mean unpleasant, but specifically means that there is a risk of harm. The context of driving on winding mountain roads at night strongly suggests danger rather than merely annoyance. Therefore, the learner should select the adjective that emphasises risk and hazard, which is "treacherous".

Step-by-Step Solution:
Step 1: Visualise the described scene: narrow, winding roads going up a mountain in the dark. Step 2: Identify the key idea: such conditions are risky and could cause accidents, so the journey is dangerous. Step 3: Evaluate "carefree". This means relaxed and without worry, which is opposite to the feeling suggested by the sentence. Step 4: Evaluate "beastly". This is informal and means very unpleasant, but does not necessarily convey danger or risk. Step 5: Evaluate "obnoxious". This refers to something extremely unpleasant or offensive, usually related to behaviour or smell, not to physical travel conditions. Step 6: Evaluate "treacherous". This means full of hidden dangers, which fits perfectly with winding mountain roads at night.

Verification / Alternative check:
A good verification method is to check how these adjectives are commonly used. Phrases like "treacherous journey", "treacherous roads", or "treacherous terrain" are common in English and always imply danger. Phrases like "carefree journey" or "obnoxious journey" are either contextually opposite or awkward. Therefore, matching collocation and meaning both confirm that "treacherous" is correct.

Why Other Options Are Wrong:

• Carefree: Suggests that the driver feels relaxed and unconcerned about danger, which contradicts the idea of risky mountain roads at night.
• Beastly: Only suggests something is very unpleasant; it does not specifically express danger and is usually informal.
• Obnoxious: Refers to something highly offensive or annoying, typically not used to describe physical road conditions.
• Treacherous: Correctly describes something that is hazardous or full of hidden dangers, which matches the given context.

Common Pitfalls:
Students sometimes choose a word that simply feels negative instead of one that matches the specific type of negativity implied. While "beastly" and "obnoxious" both sound negative, they do not carry the sense of danger. The exam expects the learner to catch the nuance that mountain driving on winding roads at night is risky and focus on that aspect, not just on discomfort or annoyance.

Final Answer:
The most suitable word to fill the blank is treacherous.