Final answer:
The correct answer is B: Because he was calm and collected in spite of the emergency, he was able to help everyone to safety.
Step-by-step explanation:
The correct answer is: Because he was calm and collected in spite of the emergency, he was able to help everyone to safety.
A complete sentence must have a subject (who or what the sentence is about) and a predicate (what the subject is doing or being). In the given options, only the sentence 'Because he was calm and collected in spite of the emergency, he was able to help everyone to safety' has both a subject (he) and a predicate (was calm and collected in spite of the emergency, was able to help everyone to safety), making it a complete sentence.
Therefore, the correct option is the sentence in choice B.
Learn more about Complete sentences in English