An economist noticed that people in nations with more TV sets have a higher life expectancy. That is, she noticed that there is a strong positive association between mean longevity of people in a given country and the total number of TV sets in that country. Select the most appropriate cause-and- effect explanation for this observation. a) There are only two cause-and-effect relationships: more TV sets cause higher life expectancy, or higher life expectancy causes more TV sets. b) Perhaps more TV sets cause higher life expectancy, higher life expectancy causes more TV sets, or both could be caused by a lurking variable such as the TV sets brand. c) There is only one cause-and-effect relationship: more TV sets cause higher life expectancy. d) There is only one cause-and-effect relationship: higher life expectancy causes more TV sets. e) Perhaps more TV sets cause higher life expectancy, higher life expectancy causes more TV sets, or both could be caused by a lurking variable such as the wealth of the