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.

Fact 1: the mass of an object causes the gravitational force exerted by that object. 
Fact 2: Gravity accelerates mass.
gravitational force accelerates objects.

Fact 1: a plant requires nutrients to grow. 
Fact 2: Legumes are typical of that type of plant.
legumes require nutrients to grow.

Fact 1: drought is when amount of precipitation decreases. 
Fact 2: Some researches have reported that acid precipitation decreases crop productivity.

Crop productivity decreases during a drought.