What rare quality do these words all have in common?

CHECKBOOK, BEDECKED, COOKBOOK, EXCEEDED

This is a tough one, but interesting. If anyone can come up with the answer to this one, I'll give them ten points instead of five!

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What very peculiar property do the following words have in common?

cover, dust, left, transparent

 

What rare characteristic do the following words all share?

Devil
Sinned
God
Warts

What rule defines the following sequence of numbers?

5, 2, 2.5, 2, 2

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Hint: This problem will be easier for people from the USA!

What peculiar property do these words share?

Rugged, Ague

Where does 13 belong in this ordered sequence of numbers?



8, 11, 5, 4, 9, 1, 7, 6, 10, 3, 12, 2