One weakness of natural experiments is:

Natural experiments are characterized by the fact that the researcher does not manipulate any variables; instead, they observe the effects of naturally occurring changes. One of their significant weaknesses is that they can be challenging to replicate. This difficulty arises because the conditions that lead to the natural experiment may not occur again in the same way, making it hard to reproduce the study. Replicability is a key aspect of scientific research, as it helps to confirm findings and enhance the validity of conclusions.

In contrast, some other options present aspects that do not align with the typical characteristics of natural experiments. For instance, natural experiments often have lower control over variables compared to laboratory or controlled experiments, which is why the option regarding high levels of control does not apply. Additionally, establishing a clear cause-and-effect relationship is convoluted in natural experiments, as external factors may interfere with the observed outcomes. Lastly, while natural experiments sometimes require fewer participants, this is not a guaranteed trait and doesn't fundamentally address the inherent complexities and limitations of natural experiments.