know how deep the river got when it rained. know how far the river bed is from a town. have accurate notes describing the location. have the weather records for the past few months.
I gave my students this multiple choice question: A scientist was digging for dinosaur bones in a dry river bed. It started to rain and the scientist had to leave the area. If another scientist wanted to continue digging in the same place, he would have to

Only one answer is correct among these 4 choices:
- know how deep the river got when it rained.
- know how far the river bed is from a town.
- have accurate notes describing the location.
- have the weather records for the past few months.

Could you tell me which one is correct?

have accurate notes describing the location.