There are many different types of scientific investigations. which of the following forms requires the identification and control of variables?
a.
observational field studies
b.
collection of specimens
c.
model-building
d.
laboratory experiments

 D. Laboratory experiments

Explanation:  Laboratory experiments are the foundations of scientific investigations.

We cannot reach to the final conclusion without performing rigorous experiments. In order to identify and control different kinds of variable, we perform experiments.

And moreover someyimes, the conclusions cannot be made without modifications in the procedure. That is where, we need to perform laboratory experiments.

answer

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