A biologist was in a forest when he came across a family of squirrels hiding nuts for the winter. The biologist was interested in this behavior, so he stayed and watched the squirrels for a few hours. He recorded what he observed in a notebook. Which of the following explains why this type of research is NOT considered an experiment? Group of answer choices

The biologist observed the squirrels and did not test variables.

The biologist came across the squirrels by chance and had no formal plan.

The biologist did not observe the squirrels for long enough to collect data.

The biologist did not collect valid data on the different species of squirrels present