Surveys show that very few of today's 85-90-year-olds are left-handed. Sociologists believe that this is because 80 years ago, children were forced to use their right hands if they would be beaten if they ate or wrote with their left hands. What assertions can be strengthened by this investigation? ['Habits are the product of genetic advantages and social stress.', 'In the past, people have different social attitudes with left or right hands.', 'Because right-handed people can live longer, parents force left-handed children to change their habits.', 'Using the right hand is smarter. It is scientifically untenable.']