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: Mating is generally preceded by courtship. 
Fact 2: For example, a black rooster and a white hen mate, and the resulting offspring are gray.
answer:
courtship can result in offspring.


question:
Fact 1: Protozoa make humans sick when they become human parasites. 
Fact 2: Malaria parasites are transmitted by mosquitos.
answer:
Malaria is a protozoa that make humans sick.


question:
Fact 1: optical tools are used for observing materials up close. 
Fact 2: Magnification glass scales for optical comparators.
answer:

magnification glass can be used to observe materials up close.