The chance that a particular event will occur is called the events

weathering is the answer.

chert is a sedimentary rock composed of microcrystalline or cryptocrystalline silica. with this little bit of information, you can come to the conclusion that your answer is c.  

explanation:

it's diluted or concentrated

in a diluted solution, you can add a lot more solute but in concentrated only a little more can be added