For which method of determining population size is the population not aware of the sampler’s presence? a. mark/recapture b. direct observation c. sampling d. indirect observation

Option D is correct.

d. indirect observation

Indirect observation is the method of determining population size is the population not aware of the sampler’s presence.

In this way we cannot measure the correct number of population.

Indirect observation is an observational technique where some records of past behavior is used than observing behavior contemporaneously.

So when determining population size if the population is not aware of the sampler's presence then it will be called as indirect observation.