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.

Example Input: Fact 1: a delta is formed by deposition of sediment at the mouth of a river by water fanning out. 
Fact 2: Erosion is responsible for wearing down exposed places and depositing sediment in level places.
Example Output: a delta is formed by erosion.

Example Input: Fact 1: Reproduction is the process by which organisms give rise to offspring. 
Fact 2: Sex equals reproduction.
Example Output: sex is the process by which organisms give rise to offspring.

Example Input: Fact 1: an animal requires warmth for survival. 
Fact 2: Light and heat and warmth are basic necessities for survival.
Example Output:
Heat is necessary for the survival of animals.