When, on a particular shopping trip, a consumer purchases an item which he previously had no intention of purchasing, this sale is called an "impulse purchase. " The objects of impulse purchases are occasionally essential items (i. e. items that satisfy basic subsistence needs), but much more frequently are luxury or non-essential items. Researchers have determined that, at the end of a shopping trip, a consumer is much more excited if she has bought a luxury item on an impulse purchase, than if she had made no impulse purchases. If the information above is true, and if the researchers' investigation was properly conducted, then which of the following must also be true? ['The researchers had a reliable way to determine whether the consumer had planned to buy the luxury or non-essential item he purchased on that trip.', 'The impulse purchase of luxury or non-essential item is more exciting than the impulse purchase of an essential need.', 'Consumers seeking a high level of excitement often make impulse purchases.', 'A consumer who, for whatever reason, is not able to purchase an item she had planned to buy is necessarily disappointed.']