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: Behaviors that improve fitness increase through natural selection. 
Fact 2: Darwinism is strictly, selection theory.
Example Output: behaviors that improve fitness increase through Darwinism.

Example Input: Fact 1: skin is used for protecting the body from harmful substances. 
Fact 2: Contamination is the unintended presence of harmful substances or microorganisms in food.
Example Output: The skin is used for protecting the body from contamination.

Example Input: Fact 1: a warm front causes cloudy and rainy weather. 
Fact 2: If warm air is advancing on cold air, the front is designated a warm front.
Example Output:
Warm air advancing on cold air can lead to cloudy and rainy weather.