Mr. Reed made up his mind to devote all he had to ________ some schools for poor children.

A．set up

B．setting up

C．have set up

D．having set up

某个地区某个年份人口死亡率骤然升高，产生这一现象的原因可能是[ ]

A、环境污染比较严重

B、医疗卫生条件下降

C、经济发展速度减慢

D、遭遇大的自然灾害