阅读理解。阅读下面短文，从每题所给的A、B、C、D四个选项中，选出最佳选项。
Nowadays some students in middle school date with their classmates．According to a new study from the University of Georgia, those students have much worse study skills and are four times more likely to stop schooling．They use twice as much alcohol and tobacco than their single classmates．
"Romantic relationships are a trademark of adolescence, but very few studies have examined how adolescents differ in the development of these relationships," said Pamela Orpinas, study author and professor in the College of Public Health and Head of the department of Health Promotion and Behaviour．
Orpinas followed a group of 624 students over a seven-year period from 6th to 12th grades．
Each year, the group of students completed a survey indicating whether they had dated and reported the frequency of different behaviours, including the use of drugs and alcohol．Their teachers completed questionnaires about the students7 academic efforts． He found some students never or hardly ever reported dating from middle to high school, and these students had consistently the best study skills according to their teachers．Other students dated infrequently in middle school but increased the frequency of dating in high school．
