It’s reported that a plane with five people crashed into the mountain several days ago.A.

问题补充：

It’s reported that a plane with five people crashed into the mountain several days ago.

A. on board

B. on the board

C. in board

D. in the board

答案：

(答案→)A. on board

B. on the board

C. in board

D. in the board

解析：on board意为“在船上、在飞机上”，为固定的介词短语。没有B、C、D这样的搭配。