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: a delta is formed by deposition of sediment at the mouth of a river by water fanning out. 
Fact 2: Sand is an example of a clastic sediment.

A: a delta is formed by deposition of sand at the mouth of a river by water fanning out.
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Q: Fact 1: Viruses cause many human diseases. 
Fact 2: Human viruses are created by natural process.

A: Something created by a natural process  cause many human diseases.
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Q: Fact 1: Fertilization occurs when a sperm and an egg fuse. 
Fact 2: Fertilization is complete when the sperm and egg nuclei fuse.

A:
Fertilization occurs when a sperm and nuclei fuse.
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