判断主题或细节：The underlilned sentence is the topic sentence of the paragraph.
A pessimistic attitude may seem so deeply rooted as to be permanent.  I have found,  however, that pessimism is escapable. Pessimists can in fact learn to be optimists,  and not through mindless devices like whistling a happy tune or mouthing platitudes  ("Every day, in every way, I'm getting better and better:'), but by learning  a new set  of cognitive skills. Far from being the creations of boosters or of the popular media,  these skills were discovered in the laboratories and clinics of leading psychologists and  psychiatrists and then rigorously validated.
A、正确
B、错误