2- Scientists do different experiments to, animal's intelligence.
b. measure
c. weigh
d. add
a. count​

b. measure

Explanation:

An experiment can be defined as an investigation which typically involves the process of manipulating an independent variable (the cause) in order to be able to determine or measure the dependent variable (the effect).

Hence, an experiment can show how changing a variable can affect behavior.

This ultimately implies that, an experiment can be used by scientists to show or demonstrate how a condition causes or gives rise to another i.e cause and effect, influence, behavior, etc in a sample.

Simply stated, the main purpose or essence of an experiment is to measure the variables involved.

Hence, scientists do different experiments to measure animal's intelligence.

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