题目

 --- _______ that he picked up French? --- It was in 2010 _______ he traveled in France.   A. Was it when; that        B. When was it; that  C. Was it when; when       D. When was it; when 答案：  D关于B和E的比较，以下说法正确的是（    ）　 A．磁感应强度B和电场强度E都是矢量B．磁感应强度B和电场强度E都由场本身决定的C．磁感应强度B和电场强度E的方向是检验电流和检验电荷在场中受力的方向D．磁感应强度B和电场强度E都是用比值来定义的