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.

Q: Fact 1: fossils are formed when layers of sediment cover the remains of organisms over time. 
Fact 2: All streams carry sediment .

A: Fossils are formed when layers of something streams carry cover the remains of organisms over time.
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Q: Fact 1: if a planet becomes too hot then that planet cannot sustain life. 
Fact 2: Life depends to a large degree on the temperature of the planet, and temperature depends in part on the distance of the planet from the sun.

A: Life cannot be sustained above a certain temperature.
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Q: Fact 1: travelling requires navigation. 
Fact 2: Navigation is a key element of space travel.

A:
space exploration is not possible without navigation.
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