—I’m sure I will get good grades (成绩) in this exam.

—If so, I believe your parents will ______ the result.

A．be satisfied with

B．be angry about

C．be bord of

D．be worried about

已知：660供电系统，变压器内阻R。=0.069Ω，变压器阻抗Xb＝0.038Ω，第一段干线电缆电阻R1=0.1071Ω，电抗X1=0.0265Ω，第二段电缆电阻R2＝0.138Ω，电抗X20.014Ω，求第二段干线电缆末端两相短路电流。