In this English grammar error-spotting question, you must identify the part of the sentence that contains an error in preposition or word choice in the sentence “What are you doing by here?” Choose the option that indicates the incorrect part.

Introduction / Context:
This question checks your ability to recognise incorrect preposition usage in everyday English sentences. The sentence given is “What are you doing by here?” broken into labelled parts, and you need to select the part that contains the error. Such questions appear frequently in competitive exams, because prepositions are often misused by learners of English even at advanced levels.

Given Data / Assumptions:

• The sentence is divided as: (1) What are (2) you doing (3) by here? (4) No Error.
• The intended meaning is to ask why or for what purpose someone is present at that location.
• Standard English uses “here” or “here for” in such contexts, not “by here.”
• We assume a neutral conversational context.

Concept / Approach:
“By” is usually used to indicate proximity, agent, or method, such as “sit by the window,” “a book by an author,” or “travel by bus.” In the sentence “What are you doing here?” the speaker is simply asking about the person's activity or purpose at that place. The preposition “by” is unnecessary and incorrect in this structure. Instead, we either omit a preposition and use “here” alone, or we change the sentence to something like “What are you doing by this place?” if we really want to use “by.” Therefore, the error lies in the phrase “by here,” which is part (3).

Step-by-Step Solution:
Step 1: Read the full sentence and understand its likely meaning: the speaker is surprised or curious about the listener's presence in this area.Step 2: Recall the standard question in English: “What are you doing here?” which does not use “by.”Step 3: Identify where “by” occurs in the given sentence. It is in part (3): “by here.”Step 4: Recognise that “by here” is not natural or necessary in this context.Step 5: Conclude that part (3) contains the error and should simply be replaced with “here.”

Verification / Alternative check:
Replace “by here” with “here” and read the sentence again: “What are you doing here?” This is a correct and very common question in English, used to ask why someone is at a particular place. None of the other parts shows any problem. “What are” is correct for forming a present continuous question, and “you doing” is the appropriate continuous verb phrase. Therefore, the only incorrect element is the unnecessary preposition “by” in part (3).

Why Other Options Are Wrong:
Part (1), “What are,” is grammatically accurate for starting a present continuous interrogative. Part (2), “you doing,” is also correct and pairs properly with “What are” to form “What are you doing.” Part (4) stands for “No Error,” which cannot be chosen because we have clearly identified an unnatural phrase requiring correction. Thus options 1, 2, and 4 are not appropriate answers.

Common Pitfalls:
Some learners may overlook the small word “by” and think the sentence sounds acceptable because “by here” is occasionally heard in informal speech. Others may suspect a different part, such as “What are,” because they are not confident about present continuous question formation. To avoid such mistakes, it is helpful to compare the sentence with the most common natural form you have heard and to remember that questions about someone's presence usually take the simple “What are you doing here?” structure, with no preposition before “here.”

Final Answer:
The incorrect part is 3, because “by here” should be replaced with “here.”