There is a saying that coming events cast their shadows before. (1) ______ it is not universally true. Something can happen within a second, and one may not (2) ______ it. (3) ______ some instances show that predictions based on certain signs have gone wrong. People generally say that natural calamities can be predicted by observing the animals. But what if animals are suffering from some disease and don’t show any signs before the event appears? They may fail to make peculiar sounds or actions about the events which are going to take place. (4) ______ some unnatural calamities that are likely to appear may forecast their shadows by some bad omens. (5) ______ we should not completely cancel out the possibilities that animals can sense certain unnatural happenings.

Select the most appropriate option to fill in blank number 3.

The correct option to fill in blank number (3) is Moreover.

Let's analyze the context of the passage step-by-step to understand why "Moreover" is the most appropriate transition word:
1. The passage starts by discussing the saying that "coming events cast their shadows before" (meaning future events can be predicted by current signs).
2. Blank (1) is followed by "it is not universally true," which introduces a contrast. Thus, a word like "But" or "However" would fit there.
3. Sentence (2) adds that "Something can happen within a second, and one may not [predict/notice] it." This supports the idea that events cannot always be predicted.
4. Blank (3) introduces a new, additional point that supports the same argument (that predictions are unreliable): "some instances show that predictions based on certain signs have gone wrong."
5. Since this sentence builds upon the previous limitation by adding another related piece of evidence supporting the same main idea, we need an additive connector.
6. Among the options:
- However and Nevertheless are adversative/confrontational transition words used to show contrast, which doesn't fit here since we are continuing the same line of reasoning.
- Therefore is used to show a result or consequence (cause and effect), but the fact that predictions have gone wrong is not a direct result of something happening in a second.
- Moreover is used to introduce additional, supporting information or arguments. It translates to "in addition to what has been said," making it the perfect fit to add another reason why the saying is not universally true.