Error spotting in a complex sentence with however: Mr. Joshi was, however, sure that the idea would never work in practice. Decide whether there is any grammatical error in any part of the sentence.

Introduction / Context:
This question checks correct use of the conjunctive adverb however, the structure of a that clause, and the phrase in practice. The sentence describes Mr Joshi's firm belief that a particular idea would fail when applied in real life. Candidates must decide whether any part of this complex sentence violates standard grammar or punctuation conventions.

Given Data / Assumptions:
- Sentence: Mr. Joshi was, however, sure that the idea would never work in practice.
- However is placed between commas after the verb was.
- The that clause explains his belief about the idea working in real life.
We assume that the sentence appears in a formal context like a report or an analysis.

Concept / Approach:
The word however can function as a conjunctive adverb inserted between commas to show contrast with previous information. It is common to place however after the verb be in such a structure. The clause that the idea would never work in practice is a correct object clause following sure, and in practice correctly refers to real world application as opposed to theory. Therefore, all parts of the sentence are grammatically acceptable and idiomatic.

Step-by-Step Solution:
Step 1: Examine the subject and verb: Mr. Joshi was. This is a correct combination of subject and past tense of be. Step 2: Look at the insertion of however: was, however, sure. The commas around however correctly mark it as a parenthetical adverbial indicating contrast. Step 3: Consider the object complement sure that the idea would never work in practice. Sure can be followed by a that clause indicating the content of belief. Step 4: The clause that the idea would never work in practice is well formed, with the modal would expressing prediction about the future from a past perspective. Step 5: The phrase in practice is standard for discussing how something performs when actually tried, as opposed to in theory. Step 6: Since no segment violates grammatical rules, we conclude there is no error in the sentence.

Verification / Alternative check:
We can slightly rephrase the sentence to test its correctness: However, Mr. Joshi was sure that the idea would never work in practice. This alternative positions however at the beginning but keeps the same basic structure and shows that the original internal placement is also legitimate. We can also remove the parenthetical commas: Mr. Joshi was sure that the idea would never work in practice, which is entirely grammatical. These checks confirm that the given sentence is correct.

Why Other Options Are Wrong:
- Error in the placement of however after was: However is often placed in the middle of a sentence with commas, and its position here is acceptable.

- Error in the clause that the idea would never work: This clause is correctly constructed and uses would to indicate a belief about an outcome, so no error exists here.
- Error in the phrase in practice: In practice is a standard phrase contrasting theory and application, so it is not wrong.
- Error in more than one part of the sentence: Because no part needs correction, claiming multiple errors is clearly incorrect.

Common Pitfalls:
Learners sometimes feel unsure about the placement of however and overcorrect by moving it unnecessarily. They may also suspect an error whenever a sentence looks slightly more formal or contains insertions with commas. It is important to recognise that not every complex sentence has a mistake. Being able to accept a well formed sentence and confidently choose No error is a crucial exam skill.

Final Answer:
Correct option: No error in the sentence.