A survey of a group of people between the ages of 75 and 80 found that those who regularly played the card game bridge tended to have better short-term memory than those who did not play bridge. It was originally concluded from this that playing bridge can help older people to retain and develop their memory. However, it may well be that bridge is simply a more enjoyable game for people who already have good short-term memory and who are thus more inclined to play. In countering the original conclusion the reasoning above uses which one of the following techniques? ['conceding the suggested relationship between playing bridge and short-term memory, but questioning whether any conclusion about appropriate therapy can be drawn', 'arguing that the original conclusion relied on an inaccurate understanding of the motives that the people surveyed have for playing bridge', 'providing an alternative hypothesis to explain the data on which the original conclusion was based', 'challenging the representativeness of the sample surveyed']