A.Encouraging high-emitting nations to take the initiative.
B.Calling on all the nations concerned to make joint efforts.
C.Pushing the current world leaders to come to a consensus.
D.Putting in effect the policies in the agreement at once.
A.Mental problems can now be found in large numbers of teenagers.
B.Teenagers' mental problems are getting more and more attention.
C.Teenagers' mental problems are often too conspicuous not to be observed.
D.Depression and anxiety are the most common symptoms of mental problems.
A.Teenagers' lifestyles have changed greatly in recent years.
B.Many teenagers resort to drugs or alcohol for mental relief.
C.Teenagers experiencing psychological problems tend to use a lot of media.
D.Many hitherto unobserved youngsters may have psychological problems.
A.Their behaviors can be an invisible threat to society.
B.Their behaviors do not constitute a warning signal.
C.Their behaviors do not tend towards mental problems.
D.Their behaviors can be found in almost all teenagers on earth.