Answer:
Option C would likely produce the most representative sample of the population of smartphones made by the company. By testing every 500th smartphone off the production line, the manufacturer can ensure that they are selecting a random sample of smartphones from throughout the production process. This can help to account for any variations or changes that may occur in the manufacturing process over time.
Option A, testing the first smartphone off the production line each day, may not be representative of the entire production run since the first smartphone may not be representative of the rest of the batch. Similarly, option B, testing the last 1000 smartphones produced each month, may not be representative of the entire production run as there may be variations in quality and safety standards throughout the month.
Option D, testing every smartphone made on Wednesday, would likely not produce a representative sample as it may not account for any variations or changes that occur during other days of the week.