passage 2
51.C Teenagers’ mental problems are often too conspicuous not to be observed.
52.D Many hitherto unobserved youngsters may have psychological problems
53.B Their behaviors do not constitute a warning signal.
54.A They are almost as liable to depression as the high-risk group
55.B it provides new early-warning signals for identifying teens in trouble.
adj. 有义务的,应负责的,有 ... 倾向