In the following questions, few sentences are given. Choose and mark the sentence which contains no grammatical or contextual error in it. If all the sentences are grammatically and contextually incorrect, mark "All are incorrect" option as the answer choice.

The correct answer is: The appellant was granted bail after furnishing the required surety bond.

Step-by-Step Educational Explanation:

Let's analyze each sentence to identify any grammatical or contextual errors:

1. Option A: "The surgeon insisted the attendants to vacate the hall before the procedure began."
Grammatical Error: The verb "insist" when followed by a clause usually takes a subjunction like "that" followed by a subjunctive verb or standard clause (e.g., "insisted that the attendants vacate..."), or it takes the preposition "on" followed by a gerund (e.g., "insisted on the attendants vacating..."). Using an infinitive ("insisted the attendants to vacate") is grammatically incorrect.

2. Option B: "He has been relocated to the southern depot since the strike ended last month."
Grammatical/Contextual Error: Using the present perfect tense ("has been relocated") with "since the strike ended last month" can sound awkward depending on strict contextual rules, but more importantly, let's examine Option D which is standard legal/formal usage.

3. Option C: "Neither of the two pilots were available for debriefing after the flight landed."
Grammatical Error: The pronoun "Neither" is singular when referring to one of two choices and requires a singular verb. Therefore, "were" should be corrected to "was" ("Neither of the two pilots was available...").

4. Option D: "The appellant was granted bail after furnishing the required surety bond."
Grammatical Status: This sentence is completely correct. "The appellant" (singular subject) pairs correctly with "was granted" (passive voice, simple past), and "after furnishing the required surety bond" is a prepositional phrase with a gerund phrase used flawlessly.

Therefore, the sentence containing no grammatical or contextual error is Option D.