In the following question, out of the four alternatives, select the alternative which will improve the bracketed part of the sentence; in case no improvement is needed, select the option marked "no improvement": Since when (have to start) a business been so easy?

Introduction / Context:
This grammar question tests the correct verb phrase and sentence structure for a present perfect question beginning with "Since when". The given sentence is "Since when (have to start) a business been so easy?" The aim is to produce a natural, grammatically correct English sentence that asks when an ongoing situation began. Such transformation items are common in competitive exams to check the ability to manipulate auxiliary verbs, gerunds, and word order.

Given Data / Assumptions:

• The sentence structure must begin with "Since when" and end with "a business been so easy".
• The bracketed phrase "have to start" is incorrect and needs improvement.
• The intended meaning is "Since when has starting a business been so easy?"
• The options are "has started", "have starting", "has starting", "no improvement", and "did start".
• We assume that the exam expects the most natural present perfect construction expressing surprise at how easy it has become.

Concept / Approach:
The correct target sentence in standard English is "Since when has starting a business been so easy?" Here, "starting a business" acts as a gerund phrase functioning as the subject of "has been". In the defective original, "have to start" does not fit into this structure. To reach the correct form, the bracketed phrase must change so that when substituted, the full sentence reads correctly. Replacing "have to start" with "has starting" yields "Since when has starting a business been so easy", which matches the intended pattern: auxiliary "has", gerund "starting", and main verb "been". Thus, among the exam options, "has starting" is the best repair, even though on its own it is not a complete unit.

Step-by-Step Solution:
Step 1: Identify the desired structure for such questions: "Since when has plus gerund phrase plus been so adjective". Step 2: Imagine the correct full sentence: "Since when has starting a business been so easy?" Step 3: Determine what phrase must replace the bracket to get this result. The original envelope is "Since when (X) a business been so easy?" If X is "has starting", the sentence becomes "Since when has starting a business been so easy". Step 4: Test option "has started". If we insert it, the sentence reads "Since when has started a business been so easy", which is not grammatical because "started" is a past participle and does not work as part of the subject here. Step 5: Test "have starting". Inserting that gives "Since when have starting a business been so easy", which has a mismatch between plural auxiliary "have" and singular subject "starting a business". Step 6: Test "has starting". This produces "Since when has starting a business been so easy", which is a correct and natural sentence. Step 7: Test "no improvement". Leaving "have to start" would keep the incorrect form "Since when have to start a business been so easy", which is wrong. Step 8: Test "did start". "Since when did start a business been so easy" is ungrammatical and mixes past simple auxiliary "did" with the present perfect "been". Step 9: Conclude that "has starting" is the best option, as it creates a correct present perfect structure.

Verification / Alternative check:
Compare with similar correct sentences: "Since when has living in this city been so expensive?", "Since when has running a shop been so difficult?" In each, the structure is "Since when has plus gerund phrase plus been". Substituting "starting a business" into this template gives exactly "Since when has starting a business been so easy", confirming that our transformed sentence follows a valid model. This verification supports choosing "has starting" as the improvement of the bracketed part.

Why Other Options Are Wrong:
"has started" would be correct in "Since when has he started that business", but not when the gerund phrase "starting a business" needs to be the subject of "been". "have starting" produces a subject–verb disagreement and does not conform to the standard present perfect pattern for such questions. "no improvement" would leave the sentence in an incorrect form that does not follow English usage. "did start" would require a different structure, such as "Since when did starting a business become so easy", and does not fit into the frame used in the question.

Common Pitfalls:
Many learners are unsure how to combine "since when" with the present perfect and gerunds. They may mistakenly keep the original words or choose a participle like "started" because it looks like a past form that pairs with "has". The key is to recognise that "starting a business" is the subject, while "has been so easy" is the verb phrase. Once this is clear, the need for "has starting a business been so easy" becomes evident. Precision in identifying subjects and auxiliaries is essential for mastering such questions.

Final Answer:
The sentence should be improved to "Since when has starting a business been so easy?", so the correct replacement of the bracketed part is has starting.