若境外接待社有损旅游者合法权益的行为，领队回国后必须向组团社OP如实汇报并递交可作凭证的书面单据，这些单据必须是（）。

A.领队签字确认

B.境外导游人员签字确认

C.境外接待社签字确认

D.旅游者签字确认

Fetch is the（）.

A.Distance a wave travels between formation and decay

B.Stretch of water over which a wave-forming wind blows

C.Time in seconds required for two crests to pass a given point

D.Measurement of a wave's steepness