In this sentence improvement question, you must choose the alternative that makes the bracketed part grammatically correct. The sentence is: "Someone must (being) killed." Which option best replaces the bracketed word to form a correct English sentence?

Introduction / Context:
This question checks your understanding of passive voice and perfect aspect when used with modal verbs such as must. The original sentence Someone must being killed is ungrammatical, and you must choose the correct auxiliary sequence to express a strong conclusion about a past event. Sentence improvement items like this are very important in competitive exams because they test both grammar and familiarity with natural English patterns.

Given Data / Assumptions:

• The given sentence is: Someone must (being) killed.
• The subject Someone is indefinite but singular in sense.
• The verb phrase is in passive voice and refers to an event already completed.
• Options include have been, has been, been and no improvement.

Concept / Approach:
In English, when a modal verb such as must expresses deduction or logical conclusion about a past action in passive voice, the correct pattern is must have been plus past participle. The verb killed is the past participle of kill. Therefore, the complete structure should be must have been killed. The auxiliary being is used in progressive passive forms like is being killed or was being killed, but it does not fit directly after must without have. You must correctly combine modal, perfect and passive elements in the right order.

Step-by-Step Solution:
Step 1: Identify the intended meaning: the speaker is concluding that it is almost certain that a killing has already happened. Step 2: Recall the structure for such deductions in passive voice: subject plus must have been plus past participle. Step 3: Recognise that the main verb is kill and its past participle is killed, so the full correct phrase is must have been killed. Step 4: Replace the bracketed part being with have been, so that the sentence becomes Someone must have been killed. Step 5: Check the options and see that have been is exactly the auxiliary sequence required. Therefore option A is correct.

Verification / Alternative check:
Compare with similar structures: The windows must have been broken by the storm or The letter must have been sent yesterday. Each uses must have been plus past participle to express a high degree of certainty about a past passive action. Our sentence Someone must have been killed follows the same pattern. If you tried must has been killed, it would sound unnatural because must is already a modal and does not need has. Must been killed and must being killed are both incomplete forms. This analysis confirms that have been is the correct replacement for being.

Why Other Options Are Wrong:
Has been would give the structure Someone must has been killed, which is ungrammatical because English does not place has after must; instead, must is followed by have. The word been by itself leaves the verb phrase incomplete, since must been killed is not a valid sequence. No improvement retains the original incorrect phrase Someone must being killed, which mixes modal and progressive passive in a way that native speakers never use. Therefore, only have been correctly completes the must have been killed structure.

Common Pitfalls:
Students often confuse patterns like must have been with must be being and may try to mix elements incorrectly. Another frequent issue is forgetting that modal verbs do not take has or had directly; they always pair with the base form have. To avoid these mistakes, remember that for logical conclusions about the past in passive voice the standard pattern is must have been plus past participle. Practising with multiple examples will fix this in your long term memory and help you score well in sentence improvement questions.

Final Answer:
The correct improved sentence is Someone must have been killed, so the best replacement is have been.