Correct answer - Substrate.
Answer:
In science a hypothesis is useful only if it can be <u><em>tested</em></u>.
Explanation:
In a scientific experiment, a hypothesis can be described as a tentative experiment that can be tested through observations and experimentation. The results inferred from the experiments can prove whether a hypothesis was correct or wrong. Hence, a hypothesis is a very important part for the scientific method of research. The validation of a hypothesis through experimentation brings about theories, facts, laws etc. A hypothesis is made in response to a scientific question.
<h3><u>Answer</u>;</h3>
Key
A sorting device that is useful in classifying by observation is a <u>key</u>.
<h3><u>Explanation</u>;</h3>
- <em><u>Classification key or taxonomic key is a device that is used by scientists to identify unknown organisms. </u></em>
- They are constructed so that the user gets a series of choices about the characteristics of the unknown organisms.Thus, by making the correct choice at each step, one is led to the identity of the specimen.
- Therefore<u><em>, keys can be used to identify a living organism or determine which group it belongs to</em></u> by answering questions on the key about characteristics of living things.