Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
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Question: The properties of the alkali metals are similar to each other as expected for elements in the same family.

Answer: The properties of the alkali metals are similar to each other as expected for elements in the same what?

Question: The bird ancestor that lived in trees developed wings, which is commonly associated with birds.

Answer: The bird ancestor that lived in trees developed what feature commonly associated with birds?

Question: Water is the main component of milk.

Answer:
What is the main component of milk?