The probability of an event happening can be found by finding the ratio of the number of ways an event can happen and the number of possible

outcomes

Explanation:

Probability is the study of experiments that, even when performed in very similar conditions, present results that are not possible to predict. For example, the expensive or crown experiment, even repeated, can not be predicted, since each time the coin is launched, the result may be different.

Probability associates numbers with the chances of a certain outcome happening, so that the higher that number, the greater the chance of that result occurring.  

In other words,  the probability of an event happening can be found by finding the ratio of the number of ways an event can happen and the number of possible outcomes.

well, that's easy; the answer's c, "it reduces contamination of the water and substrate of the estuary."

the answer is :