重点讲解：
1. stand down 退下；
I've already instructed my guard to stand down.
我已经叫我的保镖退下了L988xPk-8@。
2. on board 在火车（或轮船、飞机）上；
They arrived at Gatwick airport on board a plane chartered by the Italian government.
他们乘坐意大利政府的包机到达盖特威克机场4vH6.OUnu(y|O7p)[o。
3. hand over 交给；递给；
He also handed over a letter of apology from the Prime Minister.
他还递交了一封首相写的道歉信;[!6;eUi0@1[^vx]u。
4. come down 落下；
The aircraft came down in flames, and the heat fused most of the parts together into a solid mass.
飞机冒着火坠落了，大多数部件因高温而熔成一团LSwz8t5dS-。