By 2000,coal had become the fuel for more than 75% of electricity produced and only hydro continued to be another significant source suppling approximately 20%.这句话中的supply为什么要改成supplying?这句话是过去时阿所以就是说

By 2000,coal had become the fuel for more than 75% of electricity produced and only hydro continued to be another significant source suppling approximately 20%.这句话中的supply为什么要改成supplying?这句话是过去时阿所以就是说
By 2000,coal had become the fuel for more than 75% of electricity produced and only hydro continued to be another significant source suppling approximately 20%.
这句话中的supply为什么要改成supplying?这句话是过去时阿
所以就是说 如果我不用 significant source supplying approximately 20%这个句型的话 我就要把这句话改成significant source which supplied approximately 20%?

By 2000,coal had become the fuel for more than 75% of electricity produced and only hydro continued to be another significant source suppling approximately 20%.这句话中的supply为什么要改成supplying?这句话是过去时阿所以就是说
这是现在分词作定语.suppling approximately 20%=which supplied approximately 20% of electricity
By 2000,coal had become the fuel for more than 75% of electricity produced and only hydro continued to be another significant source suppling approximately 20%.
截至2000年,煤炭发电占总电量的75%以上,只有水电继续充当另一重要资源,提供了总电量的大约20%.
你的理解正确.