Each of the following can be used to make observations, except: * A calculator
A digital scale
Your sense of smell
A microscope

Calculator

Explanation:

A calculator is used to make, well calculations

You can use a scale to get information about the weight of an object, and you can observe how weight changes in relation to size etc.

For obvious reasons, you can observe different scents

Again a microscope is an observational tool

Explanation:

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