Astudent hypothesizes that a goldfish will be more active in a bowl that has red gravel than in a bowl of grey gravel. to get this hypothesis, the student places one goldfish in a bowl with red gravel and another goldfish in a bowl with grey gravel. the color of the gravel is the variable in the experiment.

The correct answer will be- independent variable.

Explanation:

A scientific experimental design must include three types of variables which are independent variable (which can be manipulated), dependent variable ( which has to be tested and depending on the independent variable) and constant variable (which is kept constant).

In the given question, since the student wants to study the difference in the activeness of the goldfish in red and grey gravels, therefore, he performed the experiment with different gravels.

In this experiment, the independent variable is the color of the gravel as it can be changed as well as the dependent variable depends on this variable.

Thus, the independent variable is the correct answer.

stratosphere: as the altitude increases, the air temperature increases. the stratosphere has a layer of ozone, called the ozone layer. this layer absorbs most of the ultraviolet radiation from sunlight. this results in the stratosphere being warmer.

clumped distribution, because you'de have all of the population gathered in a relatively small are.

it's the most common because it provides protection and a mate for reproduction

example: humans, seeweed, cattles, etc.