A study shows that smartphones can lead to unhappiness. The report analyzed a large national survey. It shows that self-esteem and happiness of 8th, 10th, and 12th graders rose during the 1990s. Then, it dropped sharply in 2012. This was the year when more than half of households in the country began to own smartphones. The report also shows that increased time spent on screens lowered the well-being of adolescents. ana is writing about popularity of cell phones. Which detail would be most useful to her?

O"A study shows that smartphones can lead to unhappiness."
O "The report analyzed a large national survey."
O"This was the year when more than half of households in the country began to own smartphones."
O"The report also shows that increased time spent on screens lowered the well-being of adolescents."