In the following sentence, identify the part that contains an error, if any: Vipul has been suffering from fever since seven days.

Introduction / Context:
This item tests correct use of prepositions in the context of duration and time. In English grammar, there is a clear distinction between since and for. Since is used before a point in time, such as a specific date or clock time, while for is used before a period or length of time, such as several days or many years. The sentence about Vipul and his fever contains a common exam trap built around this rule.

Given Data / Assumptions:

• Full sentence: Vipul has been suffering from fever since seven days.
• Part A: Vipul has been
• Part B: suffering from fever
• Part C: since seven days.
• Part D: No error
• The learner must determine which segment has the grammatical error.

Concept / Approach:
The present perfect continuous tense has been suffering is correctly used to describe an action that started in the past and continues into the present. The issue lies in the preposition used before the measure of time. The phrase seven days refers to a duration or period, not a specific starting point. Therefore, English requires for seven days instead of since seven days. If a specific day were mentioned, such as since Monday or since the first of April, then since would be correct. Recognising this rule allows us to pinpoint the error in part C of the sentence.

Step-by-Step Solution:
Step 1: Check the tense in part A, Vipul has been. This correctly begins a present perfect continuous structure. Step 2: Check part B, suffering from fever. This phrase is grammatically correct and matches the tense in part A. Step 3: Examine part C, since seven days. Here, seven days is a duration, so the correct preposition should be for. Step 4: Mentally correct the sentence: Vipul has been suffering from fever for seven days. Step 5: Confirm that with this change, the sentence becomes fully correct. Step 6: Conclude that the error lies in part C.

Verification / Alternative check:
Check the rule with more examples. We say, She has lived here for ten years, but She has lived here since 2014. In the first case, ten years is a period, so for is required. In the second, 2014 is a point in time, so since is required. Similarly, He has been working since morning versus He has been working for five hours. Applying this logic to the given sentence, seven days clearly represents a duration, confirming that for is the correct preposition and that the original phrase since seven days is wrong.

Why Other Options Are Wrong:
Option A: Vipul has been is appropriate as an introduction to the present perfect continuous tense.
Option B: suffering from fever is a correct verb phrase with the correct preposition from to indicate illness.
Option D: No error is incorrect because we have already identified a genuine mistake in part C.

Common Pitfalls:
Many learners confuse since and for because in their native languages a single preposition may cover both meanings. Another pitfall is to focus only on verb tense and ignore prepositions. To avoid these mistakes, students should remember a simple rule: since plus point in time, for plus period of time. Practising with many example sentences and carefully reading good English texts can fix this distinction in memory.

Final Answer:
The error is in part C, where since should be replaced by for, so option c is correct.