The most common elements in the Earth’s crust are rarely found on their own. They are usually found combined. Suggest why this is.

The most common element throughout the Earth’s crust that are rarely found on their own will be "Astatine".

Thus the above answer is correct.

Learn more about Astatine here:

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Because there are other elements that get in touch with it. And over time with, evolution, erosion and temperature their particles tend to mix. So what once was very common became mixed over time.

1 the 4 is sig