Can anyone help me with this?

Step-by-step explanation:

The choices for this question are

a. Double-blind study

b. Experiment

c. Sample survey

d. Observational study

The right answer would be d. Observational study, because this type of study is defined as an empirical and non-experimental research where all information is obtained by observation. When we apply this study, we try to find a cause-effect relation by observing the phenomenon as it naturally happens, that is, without interfering with the course of events like experimental investigations do.

So, in this case, Matilda is just observing, without altering anything that could influence the birds. She just sits observe and recover information, that's an observational study.

Therefore, the right answer is d.