Answer:
A.  not wearing goggles when breaking a rock with a hammer
Explanation:
You could get extremely hurt if you are not wearing goggles while doing lab work.
 
        
             
        
        
        
Answer: protons and neutrons.
The nucleus is made up of 3 subatomic particles that are protons,neutrons and electrons.  
General notation of an element is 
where, X is the Element, A is the Atomic Mass and Z is the Atomic Number
If we know the number of protons we can easily find out the atomic number of any element because Atomic Number = Number of protons in an element.
And in addition if we know the number of neutrons we can easily find out the atomic mass of an element because 
Atomic Mass = (Number of protons) + (Number of neutrons)
If we get to know the atomic number and atomic mass, we can easily tell what element is it by looking from the periodic table.
 
        
             
        
        
        
Hello!
At 
Standard Pressure and Temperature, an ideal gas has a molar density of  
0,04464 mol/L.So, we need to apply a simple conversion factor to calculate the density of Sulfur Dioxide using the molar mass of Sulfur Dioxide.

So, the Density of Sulfur Dioxide (SO₂) at STP is 
2,8599 g/LHave a nice day!