Studies estimated natural community grazing rates by measuring feeding rates of individual zooplankton species in the laboratory and then computing community grazing rates for field conditions using the known population density of grazers.在句子最后using前面是不是应该加by,因为是通...
Thank you for having taken so much trouble to help.和Thank you for taking so much trouble to help.有什么区别,前面那一句是动名词完成式的被动语态?还有上面句子的句子成分解析,特别是to help作什么成分?谢谢!