Answer – C (Using instruments that have not been calibrated).
When the integrity of an instrument’s calibration has been compromised (usually due to exposure to a shock, vibration, or physical damage), it needs to be calibrated; failure to do this inevitably leads to inaccurate measurement; this is a very common measurement error.
        
             
        
        
        
You didn't give any answer choices (i'm answering this through research and what i already know)
the first is fossilized dung, and that's not generally gastropod shells. A carbon film would be something thin, seeing as it's a film, and gastropods aren't that. A gastrolith is a stone swallowed by an animal to help with digestion, and that's also not a gastropod. 
<span>Gastropod fossils may be molds, but usually aren't. Still, they can be. It's a better answer than; film or stomach stones.</span>
        
             
        
        
        
Answer:
C. 75 percent
Explanation:
Hope the answer is correct
 
        
                    
             
        
        
        
Answer:
D. All cells must be reproduced by another cell.
Explanation:
The cell theory has a couple key components, which are as follows: 
#1. Cells are the basic unit of life.
#2. Cells have hereditary data that is passed down to their offspring.
#3. All cells come from preexisting cells.
#4. All organisms, both unicellular and multicellular, are made of one or more cells.
#5. Energy flows through cells.
#6. All cells have a similar composition.
 
        
                    
             
        
        
        
Answer:
a. Proteins
Explanation:
Chromosomes are made up of DNA tightly coiled many times around proteins