题目

British scientists are breeding a new generation of rice plants that will be able to grow. in soil con??taining salt water. Their work may enable abandoned farms to become productive farms once more. Tim Flowers and Tony Yeo, from Sussex University’s School of Biological Sciences,. have spent several years researching how crops, such as rice, could be made to grow in water that has become salty. The pairs have recently begun a three-year programme, funded by the Biotechnology and Bio??logical Sciences Research Council, to establish which genes enable some plants to survive salty condi??tions在如图所示的实验电路中，AC是锰铜合金导线，DF是镍铬合金导线，它们的直径、长度均相同且粗细均匀，B和E分别为AC和DF的中点。为了研究导体电阻的大小与长度是否有关，下列操作中正确的是 A. 第一次将AB段导线接入电路，第二次将DE段导线接入电路B. 第一次将DE段导线接入电路，第二次将AC段导线接入电路C. 第一次将AB段导线接入电路，第二次将DF段导线接入电路D. 第一次将DE段导线接入电路，第二次将DF段导线接入电路