instruction:
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.
question:
Fact 1: soil is formed by rocks eroding. 
Fact 2: Soils are formed by breakdown of rock.
answer:
rocks eroding causes them to breakdown.


question:
Fact 1: if a planet becomes too hot then that planet cannot sustain life. 
Fact 2: If a planet is too close to a star, then it will be too hot for liquid water to exist.
answer:
If a planet is too close to a star, that planet cannot sustain life.


question:
Fact 1: the type of material through which sound passes changes the speed at which sound travels. 
Fact 2: On a molecular level, a fibrous material can also slow the speed of transmission of sound.
answer:

Sound passing through a fibrous material will slow down.