A sentence, or part of the sentence, is underlined in the actual question. Four alternatives are given to improve the underlined part. Choose the correct alternative and click the button corresponding to it. In case no improvement is needed, click the button corresponding to "No improvement". The sentence is: "He is suffering from fever for a week."

Introduction / Context:
This sentence improvement question tests your understanding of English tenses, especially the present perfect continuous. The sentence "He is suffering from fever for a week" attempts to describe an illness that started in the past and has continued up to the present. You must select the option that expresses this idea correctly and naturally in standard English.

Given Data / Assumptions:

The illness began one week ago and is still ongoing now.
The phrase "for a week" indicates duration from past to present, not a single point in time.
We need a tense that connects the past with the present and emphasises continuity.
The subject is singular: "He".

Concept / Approach:
In English, the present perfect continuous tense (has been + verb-ing) is used to describe actions or states that started in the past and are still continuing. For example, "He has been working here for a year" or "She has been studying since morning." Therefore, for an illness lasting one week and still present, "He has been suffering from fever for a week" is the correct structure. The simple present "is suffering" with "for a week" is not idiomatic for this meaning.

Step-by-Step Solution:
Step 1: Recognise that the phrase "for a week" signals a period starting in the past and continuing to now. Step 2: Choose the present perfect continuous tense for such situations: has been suffering. Step 3: Examine option C: "has been suffering". This matches the required tense and fits naturally with "for a week". Step 4: Option A "was suffering" describes a past continuous action, not one that continues into the present. Step 5: Option B "had suffering" is grammatically wrong; we do not say had suffering in this way. Step 6: Option D "No improvement" would keep the incorrect structure "is suffering ... for a week", so it cannot be correct. Step 7: Option E "is suffered" is also incorrect; it tries to use a passive form that does not make sense here.

Verification / Alternative check:
Compare similar sentences: "He has been living in Delhi for five years", "She has been reading this book for two days". In each case, the present perfect continuous is used with "for" plus a period of time. If we tried "He is living in Delhi for five years", it would sound wrong. Therefore, "He has been suffering from fever for a week" is the correct and standard form, confirming that option C is right.

Why Other Options Are Wrong:
Option A was suffering shifts the action entirely to the past and does not show that he is still ill now.
Option B had suffering is ungrammatical; had is not used with suffering in this pattern.
Option D No improvement is wrong because the original tense "is suffering ... for a week" is not standard English in this context.
Option E is suffered is a passive structure and does not fit with the subject "He" and the verb suffering here.

Common Pitfalls:
Students sometimes overuse the present continuous "is ... -ing" even when a longer duration is clearly indicated. A useful rule is: when you see "for" or "since" with a time period leading up to now, think of the present perfect or present perfect continuous. Practice recognising these time expressions so that you automatically choose "has been suffering" instead of "is suffering" in such questions.

Final Answer:
The correct improved form is "has been suffering", giving the full sentence: He has been suffering from fever for a week.