We cannot accurately predict how

We cannot accurately predict how much carbon dioxide ______ by factories will remain permanently in the air.
A、released
B、to release
C、releasing
D、being released
【正确答案】：A
【题目解析】：译文：我们很难精确地预测出工厂排放的二氧化碳有多少将永远留在空气中。本题考查被动语态。二氧化碳是被工厂所排放,所以应由过去分词released修饰carbon dioxide。答案为A。