单项选择题
A、 He thinks they are beautiful. B、 He believes they can bring delight to him. C、 He thinks they are worth showing to the public. D、 He believes they are particular.
A、 Pollution of the environment. B、 A new generation of pest killers. C、 Over-killing by hunters. D、 Destruction of their natural homes.
A、 At the beginning of the 19th century. B、 At the late of the 18th century. C、 At the beginning of the 18th century D、 In the middle of the 19th century.