Hey there,
Your correct answer to this question would be of that "<span>A statement of fact that is generally accepted to be true and universal because it has always been observed to be true."
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Hope this helps you.
~Jurgen
The answer is <span>d. homologous structures.
Homologous structures are </span><span>similar structures shared by different species. For example, the anatomy of joints in bones of birds and dinosaurs, support the idea that these two groups have a common ancestor. But since these two groups are different enough to be separated into different classes, it can be concluded that they evolved from the common ancestor.</span>
It's from the Hawaiian language and means the words "shiny, glassy surface, and smooth". The type of lava you want to know is Pahoehoe lava. Lava tubes are usually floored with it.
Hope this helps! :-)