A:when did he go abroad
B:why he is going abroad
C:how soon will he be back
D:how long he will stay abroad
大气中二氧化碳浓度含量增加将会产生的后果是 ( )①海面上升 ②温带草原地区气候变干 ③腐蚀建筑物 ④皮肤癌发病率上升