In the following sentence, choose the alternative that best improves the underlined conjunction to express a repeated situation. If the sky is overcast, I take my umbrella with me.

Introduction / Context:
This question tests the correct use of conjunctions and time expressions to describe repeated or habitual actions. The speaker is talking about what they regularly do in a particular weather condition, namely when the sky is overcast. Grammar questions like this help examine whether candidates can choose the most accurate word to show frequency and pattern in conditional like sentences.

Given Data / Assumptions:
• The original sentence is: If the sky is overcast, I take my umbrella with me.• The situation describes a personal habit, not a single one time event.• The speaker takes an umbrella each time the sky is overcast.

Concept / Approach:
English provides different conjunctions and adverbs to talk about time and condition. If often introduces a condition that may or may not be fulfilled in a particular case. Whenever is more suitable when we want to express that something happens every time a condition occurs. Here, the speaker is stating a general habit that is triggered each time the sky is overcast. Therefore, whenever is more precise and natural than simple if or when in many exam oriented sentences.

Step-by-Step Solution:
Step 1: Identify the intended meaning. The speaker wants to indicate a repeated action linked to a recurring situation.Step 2: Compare options. When can refer to a specific instance or general truth, but it does not emphasise the idea of every time as strongly as whenever does.Step 3: Consider unless. Unless means except if and would change the sense of the sentence completely, which is not intended here.Step 4: Choose whenever to clearly show that each time the sky is overcast, the person takes an umbrella.Step 5: Rewrite the sentence: Whenever the sky is overcast, I take my umbrella with me.

Verification / Alternative check:
Test the sentence with other habitual statements. For example, Whenever I feel tired, I drink tea. This pattern mirrors the original sentence. Also compare If the sky is overcast, I take my umbrella with me and Whenever the sky is overcast, I take my umbrella with me. Both are grammatically possible, but in exam style usage the second version more clearly communicates a regular habit linked to repeated conditions, which is why it is preferred.

Why Other Options Are Wrong:
Option a: When the sky is overcast, I take my umbrella with me is grammatically correct but does not emphasise the recurring every time nature as clearly as whenever in many exam keys.Option b: Unless the sky is overcast, I take my umbrella with me reverses the meaning and implies that the person normally carries an umbrella, except when the sky is overcast, which is not logical.Option d: No improvement is not correct because choosing whenever provides a more accurate and textbook expression for a habitual response to a specific condition.

Common Pitfalls:
Learners often use if, when, and whenever interchangeably without thinking about subtle differences. In grammar questions, exam setters expect candidates to be sensitive to nuances like single event versus repeated event. Another common error is choosing unless simply because it looks more advanced, even when it contradicts the intended meaning. It is important to read the entire sentence and imagine the real world situation before selecting a conjunction.

Final Answer:
The most accurate improvement that shows a repeated action whenever the condition is met is: Whenever, giving the sentence Whenever the sky is overcast, I take my umbrella with me.