In this English grammar error-spotting question, identify which part is incorrect or choose the option that states that the sentence has no grammatical error: "Although he studied very hard, he could not pass the exam."

Introduction / Context:
This question is from the error spotting section of English grammar. You must examine the sentence "Although he studied very hard, he could not pass the exam." and decide whether any part contains a grammatical error, or whether the sentence is correct as a whole. Such questions test your grasp of conjunctions, clause structure, and tense consistency.

Given Data / Assumptions:

• The sentence is broken into parts: A "Although he studied", B "very hard, he", C "could not pass the exam.", and D indicates no error.
• You must choose the option that best describes where the error lies.
• We assume standard formal English usage.
• The conjunction "although" introduces a contrast between effort and result.

Concept / Approach:
The key concepts here are the correct use of the subordinating conjunction "although" and the proper structure of a complex sentence. "Although" introduces a subordinate clause that shows concession, typically followed by a main clause expressing a contrasting outcome. The verb tenses and word order in both clauses should be grammatically correct and logically connected.

Step-by-Step Solution:
Step 1: Look at Part A, "Although he studied". The structure "Although + subject + past tense verb" is perfectly correct. Step 2: Check Part B, "very hard, he". The phrase "very hard" correctly modifies the verb "studied" and is positioned naturally. The comma separates the subordinate clause from the main clause, and "he" at the start of the main clause is correct. Step 3: Examine Part C, "could not pass the exam." The auxiliary "could" with "not" correctly expresses inability in the past, and "pass the exam" is standard usage. Step 4: Consider the overall sentence: "Although he studied very hard, he could not pass the exam." This is a classic example used in grammar books to show contrast between effort and outcome. Step 5: Since each part is grammatically correct and the sentence as a whole is natural and idiomatic, there is no grammatical error. Step 6: Therefore, the correct choice is the option that states that the sentence has no grammatical error.

Verification / Alternative check:
You can compare with similar sentences such as "Although she worked hard, she did not get the promotion." The structure is identical, with "although" introducing a past tense clause followed by another past tense clause showing the unexpected outcome. There is no mismatch of tenses, no wrong preposition, and no subject verb disagreement. This comparison confirms the correctness of the given sentence.

Why Other Options Are Wrong:

• Part A: "Although he studied": Correct use of "although" with a subject and past tense verb.
• Part B: "very hard, he": "Very hard" is a proper adverbial phrase modifying "studied"; word order is acceptable.
• Part C: "could not pass the exam.": Proper modal auxiliary "could" with "not" and an infinitive verb, no error.
• There is an error in more than one part: Misleading because examination shows that all parts are grammatically sound.

Common Pitfalls:
Students sometimes overthink such questions and try to find errors where none exist. Another pitfall is confusing "although" with "in spite of" or "despite" and trying to change the structure unnecessarily. Remember that exam setters often include fully correct sentences where "No error" is the intended answer. Train yourself to accept that possibility after a careful, logical check.

Final Answer:
The sentence is grammatically correct, so the right option is Part D: The sentence has no grammatical error.