At ______, photography is a chemical process, during which a light-sensitive material is altered when exposed to light.

Evenifhisletter____tomorrow，it____toolatetodoanything.

We can hear____from the back of the room.

LastMarchthe__________ofa19thcenturycargoshipwasfoundbyanunderwaterarchaeologicalteam.

It is imperative that students _____ their term papers on time.