Marissa is testing a hypothesis through experimentation. She believes that immersing ocean coral in carbonic acid will slow the coral's growth. Which of these actions will prevent Marissa from introducing confounding variables into her experiment?

She releases cement particles into a random number of the coral samples.

She uses three different types of coral to establish her dependent variables.

She treats the coral samples identically with varying levels of carbonic acid.

She obtains her coral samples from coral reefs surrounding different continents.

C. She treats the coral samples identically with varying levels of carbonic acid.

Explanation:

She releases cement particles into a random number of the coral samples.

Doing this is uncontrolled, using a random number for anything in an experiment is a no no.

She uses three different types of coral to establish her dependent variables.

Different types of coral could react differently to the acid, always use only one dependent variable in an experiment.

She obtains her coral samples from coral reefs surrounding different continents.

It is important that the samples of coral be as close to the same as possible so that the coral variables stay constant.