Purpose:

Determine the stress level of Samantha.

Sampling procedure:

• Samantha divides up her day into three parts: morning, afternoon, and evening.
• She then measures her stress level at two randomly selected times during each part of the day

When the population from where the samples are taken is divided into categories known as 'strata', random samples are selected from each of these strata. It is known as stratified sampling.

In this example, the three parts of the day are three strata, and the level of stress is randomly taken from each strata.

Hence it is stratified sampling, and option D is correct.

Other option

A) convenience sampling

Here, the samples are taken as per the investigator's convenience such that whatever sample is readily available is recorded for observation.

B) Systematic sampling

Here the first sample is selected randomly, and subsequent ones are recorded following a systematic pattern.

C) Simple random sampling

Here, the samples are randomly drawn from the entire population.