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: the type of material through which sound passes changes the speed at which sound travels. 
Fact 2: Sounds are made by vibrating objects.

Answer: The type of material through which a vibration passes changes the speed at which it travels.


Question: Fact 1: Bioterrorism is another potential threat in the environment. 
Fact 2: Bioterrorism is a silent, but very real threat.

Answer: bioterrorism is silent.


Question: Fact 1: Placental mammals give birth to relatively large and mature infants. 
Fact 2: Humans are also placental mammals.

Answer:
Humans give birth to relatively large and mature infants.