Improve the following sentence, if necessary, by choosing the most appropriate option: "Ramesh is working in this factory for the past three months."

Introduction / Context:
This sentence improvement item tests correct tense usage when describing an action that started in the past and continues up to the present. Examinations frequently ask about the present perfect continuous tense, especially with duration phrases such as "for the past three months" or "since January". The wrong use of present continuous with "for the past three months" is a typical learner error.

Given Data / Assumptions:
- Original sentence: "Ramesh is working in this factory for the past three months."
- Ramesh started working three months ago and is still working there now.
- The phrase "for the past three months" clearly refers to a continuous period leading up to the present moment.
- We must keep the meaning but correct the tense form if needed.

Concept / Approach:
When an action began in the past and continues up to the present, English generally uses the present perfect continuous tense: "has been working", "has been living", and so on. The present continuous "is working" is not normally combined with a completed duration such as "for the past three months". Instead, present continuous is used for actions happening right now. Therefore the correct structure is "Ramesh has been working in this factory for the past three months."

Step-by-Step Solution:
Step 1: Identify the time expression "for the past three months" which signals duration up to now. Step 2: Recognise that the action of working started in the past and is still going on. Step 3: Choose present perfect continuous: "has been working". Step 4: Replace "is working" with "has been working" and keep the rest of the sentence unchanged. Step 5: Read the improved version: "Ramesh has been working in this factory for the past three months."

Verification / Alternative check:
Check each option. Option B "has been worked" is wrong because "worked" appears in passive form and does not match the intended active meaning; Ramesh is doing the work, not being worked by someone. Option C "had worked" is past perfect and normally refers to a time before some other past event, not a situation continuing into the present. "No improvement" would leave "is working for the past three months", which sounds unnatural. Therefore only option A matches the correct tense and aspect.

Why Other Options Are Wrong:
- "has been worked": incorrect voice; this makes Ramesh an object rather than the doer of the action.
- "had worked": suggests that his time in the factory is finished before another past point, which is not given in the sentence.
- "No improvement": keeps a tense form that conflicts with the duration phrase.

Common Pitfalls:
Students often combine the present continuous tense with "for" or "since" because they translate directly from their mother tongue. Remember that in standard English, an action which began in the past and still continues usually needs present perfect or present perfect continuous, especially with "for" and "since". A safe rule is: use "has been verb ing" with ongoing actions and clear duration.

Final Answer:
The correct improved sentence is Ramesh has been working in this factory for the past three months.