The writer wants Sentence 4 to serve as a conclusion that is precise and appropriately qualified. Which version best meets that purpose?

1A field notebook is often treated as a place to store observations after they have been made. That description is incomplete. [Sentence 1] A useful notebook records not only what an observer thinks happened but also where the observer hesitated.

2Consider a student identifying birds during a wetland survey. Writing "three marsh wrens" produces a clean data point. Writing "three small brown birds, probably marsh wrens; calls heard, markings partly obscured by reeds" preserves more information. [Sentence 2] The second entry may look less certain, but it gives a later reader evidence for evaluating the identification.

3Uncertainty can also reveal patterns in the method itself. If several questionable observations occur near dusk, the problem may be light. If uncertainty clusters around one species pair, the identification guide may need a clearer comparison. [Sentence 3] Notes about doubt can therefore improve both individual observations and the design of later fieldwork.

4[Sentence 4] Scientific records become more trustworthy when they show the limits of observation as carefully as they show the observations themselves.