【单选题】图 10-15 中 A 、 B 、 C 三点都在匀强电场中,已知 AC ⊥ BC ,∠ ABC = 60 °, BC = 20cm .把一个电量 q = 10 -5 C 的正电荷从 A 移到 B ,电场力做功为零;从 B 移到 C ,电场力做功为 -1.73 × 10 -3 J ,则该匀强电场的场强大小和方向是 [ ]
【简答题】We have received your letter of 15th July, informing us that the sewing machines we shipped to you arrived ______ a damaged condition ______ account of imperfectness of our packing.
【简答题】We have received your offer Oil June 20th,2009. We regret that we cannot accept it because of the terms of delivery. We made it clear in our letter that the 500 pairs of shoes should arrive here by Ju...