The passage is primarily about______.

A．Their letters of application often get no response.
B．Letters of acknowledgement carry no explanation.
C．Letters of acknowledgement sound impersonal.
D．Vacancies are set aside for friends by employers.

A．raising the world's temperature only a few degrees would not do much harm to life on earth
B．lowering the world's temperature merely a few degrees Would lead many major farming areas to disaster
C．almost no temperature variations have occurred over the past decade
D．the world's temperature will remain constant in the years to come