Answer :
Final answer:
The complement of the event 'fewer than 84 of the 250 phone batteries were defective' is 'at least 84 batteries were defective', covering all possible outcomes not included in the original event. So, the correct option is B.
Explanation:
The question asks to identify the complement of a specific event regarding phone batteries. In probability, the complement of an event is an event that represents all outcomes that are not in the original event. If the given event is 'fewer than 84 of the 250 phone batteries were defective', then the complement of this event would include all the scenarios where this condition is not met. This means that the number of defective batteries must be 84 or more.
Therefore, the correct option here is: b) at least 84 batteries were defective. This is because the original event describes the number of batteries being defective as less than 84, and the complement must cover the rest of the possible outcomes which are 84 or more being defective.
