Which of the following is TRUE regarding observational measures of well-being in studies of happiness and life satisfaction? Options: A) Observational measures of well-being are now the most widely used assessment tool in most studies. B) Observational measures of well-being are rarely used in studies of happiness and life satisfaction. C) Observational measures of well-being are the least effective assessment tool in studies of happiness and life satisfaction. D) Observational measures of well-being are no longer considered relevant in studies of happiness and life satisfaction.