In the following sentence improvement question, choose the correct verb form to replace the bracketed part in the sentence: We (has finished) our lunch half an hour ago.

Introduction / Context:
Sentence improvement questions often focus on tense consistency and subject verb agreement. The sentence We has finished our lunch half an hour ago clearly sounds wrong to a fluent speaker. The phrase half an hour ago is a clear marker of a completed action in the past, and English grammar requires a matching past tense structure. The task here is to choose the most appropriate replacement for the incorrect verb phrase has finished so that the sentence becomes natural and grammatically correct.

Given Data / Assumptions:

• Original sentence: We has finished our lunch half an hour ago.
• Bracketed part to improve: has finished.
• Options: finished, will have finished, had finished, No improvement.
• We note the time expression half an hour ago, which clearly places the action in the past.

Concept / Approach:
When a sentence contains an explicit past time marker such as yesterday, last week, or half an hour ago, the standard tense used is simple past, not present perfect or future perfect. The subject We is plural, so in simple past the correct form is We finished. The present perfect form We have finished could be possible in some contexts, but here has is incorrect because it does not agree with We, and the presence of ago favours simple past. The other options either express future time or past perfect, neither of which fits this simple context.

Step-by-Step Solution:
Step 1: Identify the subject and tense marker. The subject is We and the time expression half an hour ago indicates completed past time. Step 2: Recognise that with ago, English normally uses simple past, so the basic structure should be We finished our lunch half an hour ago. Step 3: Examine option A, finished, which leads to We finished our lunch half an hour ago, a correct and natural sentence. Step 4: Examine option B, will have finished, which suggests a future perfect situation and would require a future reference point, not ago. Step 5: Examine option C, had finished, which is past perfect and usually needs another past event for comparison, such as before we left, which is not present here. Step 6: Examine option D, No improvement, which would wrongly retain has finished and keep the subject verb disagreement and tense issue. Step 7: Conclude that finished is the correct choice to replace has finished.

Verification / Alternative check:
Compare sentences in standard usage. We finished our lunch half an hour ago is exactly how a fluent speaker would describe a completed action with a clear time reference. We have finished our lunch half an hour ago is rarely used and is considered awkward, because present perfect does not normally combine with a specific past time expression using ago. Will have finished and had finished both require more complex contexts that are not given in the sentence. This confirms that the simple past finished is the proper correction.

Why Other Options Are Wrong:
Will have finished is wrong because it refers to completion by a point in the future, and contradicts the past marker ago. Had finished is wrong because past perfect is used when one past action is completed before another past action, which is not mentioned here. No improvement is wrong because We has finished is incorrect both in agreement and in typical tense usage with ago. Therefore, these options cannot be accepted.

Common Pitfalls:
Learners sometimes overuse present perfect and past perfect because they sound more advanced, ignoring the fact that simple past is correct and natural with explicit past time markers. Another common mistake is not checking subject verb agreement carefully and overlooking that We requires have, not has. When you see ago in an exam sentence, it should strongly signal simple past, which is a quick way to avoid confusion while selecting the correct answer.

Final Answer:
The correct improvement is to use simple past, so the sentence becomes We finished our lunch half an hour ago. The answer is finished.