环境人口容量具有不确定性，是因为

①资源总数不确定      ②科学技术水平不断提高   ③人口消费水平不断增长   ④人口增加对环境影响程度不确定

A．①③

B．②④

C．①②③

D．②③④

After the war, a new school building was put up __________there used to be a theatre.     [ ]

A. that

B. where

C. which

D. when