Improve the bracketed part of the sentence by choosing the best alternative. If no improvement is required, select "No improvement". Sentence: Fans (queue) for the concert tickets since early morning.

Introduction / Context:
This sentence improvement question tests your understanding of tense and aspect, especially the present perfect continuous tense used for actions that started in the past and continue up to the present. The sentence describes fans lining up for concert tickets "since early morning", which clearly signals a continuous action from a specific point in the past until now. You must choose the verb form that best expresses this idea.

Given Data / Assumptions:

• Original sentence: "Fans (queue) for the concert tickets since early morning."
• Subject: "Fans" (plural).
• Time marker: "since early morning", indicating an action started in the past and still continuing.
• Options: has queued up, have had queued, have been queuing up, no improvement.

Concept / Approach:
The structure "since + point in time" usually pairs with present perfect or present perfect continuous tense. When the focus is on an action that has continued over a period, we prefer the present perfect continuous: "have been + verb ing". Here, the action of queuing (standing in line) has been in progress from early morning until now, so "Fans have been queuing up" is the most accurate and natural form. Other options either use the wrong auxiliary, the wrong tense, or an incorrect compound form.

Step-by-Step Solution:
Step 1: Recognise that the subject "Fans" is plural, so any auxiliary must agree in number. We need "have", not "has".Step 2: Note the phrase "since early morning". This indicates that the action started earlier in the day and continues into the present, which points to present perfect continuous tense: "have been queuing".Step 3: Examine option C, "have been queuing up". This is exactly the present perfect continuous form for a plural subject and a dynamic verb like "queue". It shows ongoing action from the past until now.Step 4: Examine option A, "has queued up". It uses "has", which is singular, but the subject "Fans" is plural, so this breaks subject verb agreement. It also uses a simple present perfect form, not continuous.Step 5: Examine option B, "have had queued". This is an incorrect and awkward compound form that is not used in standard English for this meaning.Step 6: Option D, "no improvement", would accept the bare "queue" form, which is ungrammatical in this context. Therefore, option C is the only correct improvement.

Verification / Alternative check:
Insert option C into the sentence: "Fans have been queuing up for the concert tickets since early morning." This reads naturally and matches the pattern used in everyday English to describe ongoing queues or lines. Compare with other examples: "Students have been waiting outside since dawn", "People have been working on this project since January". Both use present perfect continuous with "since" plus a point in time, reinforcing that this is the right structure here as well.

Why Other Options Are Wrong:
Option A fails due to subject verb disagreement and does not emphasise the ongoing nature of the action. Option B is simply not a valid construction in this context; "have had queued" does not express a clear tense or aspect and sounds incorrect. Option D is wrong because leaving the verb as just "queue" is not a complete tense form and does not integrate properly with "since". It would need an auxiliary to be grammatically complete.

Common Pitfalls:
Learners sometimes forget that "since" usually calls for a perfect or perfect continuous construction, not a simple present or simple past form. Another frequent error is choosing the wrong auxiliary ("has" instead of "have") when the subject is plural. A practical tip is to memorise the patterns "have/has been + ing" for ongoing actions since a point in time, and always check agreement between the auxiliary and the subject.

Final Answer:
The best improvement is "have been queuing up", so option C is correct.