In this sentence improvement question, choose the best alternative if any: You will be late if you do not leave now.

Introduction / Context:
This question tests your knowledge of basic conditional sentence patterns. In English, the first conditional is used to talk about real and possible future situations. It follows the pattern If plus present simple in the condition clause and will plus verb in the main clause. Recognising this pattern helps you see whether a sentence is already correct or needs improvement.

Given Data / Assumptions:
- Original sentence: You will be late if you do not leave now. - Underlined structure is the whole sentence. - Options include variations of the verb in the if clause. - The intended meaning is a warning about a possible future result.

Concept / Approach:
The correct first conditional structure is: If you do not leave now, you will be late. The sentence in the question simply reverses the order of clauses, which is also acceptable: You will be late if you do not leave now. Both orders are grammatically correct and common in everyday English. Therefore, the original sentence is already correct and does not need any change.

Step-by-Step Solution:
Step 1: Identify the two parts of the condition: You will be late (result clause) and if you do not leave now (if clause). Step 2: Check the tense in the if clause: do not leave is present simple, which is correct for a real future condition. Step 3: Check the tense in the main clause: will be late, which is correct for the future result. Step 4: Confirm that the overall pattern matches the first conditional structure. Step 5: Evaluate the suggested changes and see that none improves the sentence. Step 6: Therefore, choose No improvement.

Verification / Alternative check:
Rewrite the sentence with the if clause first: If you do not leave now, you will be late. This is a textbook example of a first conditional. If we replace do not leave with left (as in if you left now, you would not be late), the meaning changes to a different conditional pattern. The original, however, expresses a real future possibility based on a present decision, so the first conditional is appropriate and correctly used.

Why Other Options Are Wrong:
Will not leave now in option A produces if you will not leave now, which is not standard in this context. Did not leave now in option B mixes past tense with now, creating a tense clash. Left now in option C suggests a different conditional structure and changes the meaning of the sentence.

Common Pitfalls:
Candidates sometimes think that every sentence in a grammar question must contain an error. This leads them to modify correct conditionals unnecessarily. To avoid this, always check whether the existing pattern fits one of the standard conditional structures. If it does and the meaning is clear, it is often safest to choose No improvement.

Final Answer:
The sentence is already correct, so the best choice is No improvement.