Combine the given two facts to write a concluding fact. Note that there should be some parts of the first and second facts that are not mentioned in this conclusion fact. Your combined fact should be the result of a chain between the two facts. Chains form when two facts connect together to produce a concluding fact. An example of a chain is: "pesticides cause pollution" (fact1) + "pollution can harm animals" (fact2) → "pesticides can harm animals" (conclusion fact). Parts of the concluding fact overlap with the first and the second fact. To construct such a  concluding fact, a useful way is to borrow the subject from one fact and the ending conclusions from another fact.
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Question: Fact 1: Birds are endothermic tetrapod vertebrates. 
Fact 2: Class Aves is for the birds, literally.

Answer: Animals in the class aves are endothermic tetrapod vertebrates.


Question: Fact 1: an egg requires warmth to survive. 
Fact 2: Heat and warmth help other gift plants.

Answer: an egg requires heat to survive.


Question: Fact 1: Passive immunity lasts only as long as the antibodies survive in body fluids. 
Fact 2: Inside the body, blood is normally a fluid.

Answer:
passive immunity lasts only as long as the antibodies survive in blood.