Scientific investigations that involve some kind of testing will make use of observations. generally speaking making observations is the first step of the scientific method.
        
             
        
        
        
Acetylcholine..
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Answer:
All living things contain carbon in some form. Carbon is the primary component of macromolecules, including proteins, lipids, nucleic acids, and carbohydrates. Carbon's molecular structure allows it to bond in many different ways and with many different elements.
Explanation: