Which one of the following is not an observational study? Question content area bottom Part 1 Choose the correct answer below. A. Randomly selected airline pilots are asked about their flying experience. B. Randomly selected automobile seatbelts are tested for their breaking points. C. Randomly selected robes are coated with a flame retardant and then tested for flammability. D. Randomly selected cigarettes are tested for the amounts of nicotine that they contain