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: dew is formed when water vapor condenses over night. 
Fact 2: Dew begins to evaporate when the temperature reaches the dew point.
answer:
condensed water vapor evaporates at certain temperatures.


question:
Fact 1: All life relies on a relatively narrow range of pH, or acidity. 
Fact 2: Biochemical reactions are catalyzed by enzymes that have very narrow ranges of optimum pH values.
answer:
All life relies on a relatively narrow range of environment partly do to need of Biochemical reactions being catalyzed by enzymes.


question:
Fact 1: an image in a mirror is formed by reflecting light. 
Fact 2: Indirect light is refracted or reflected light.
answer:

a mirror image is formed by indirect light.