The average mass of a carbon atom is 12.011. assuming you were able to pick up only one carbon unit, the chances that you would randomly get one with a mass of 12.011 is

The probability of getting a carbon atom with mass 12.011 is zero.

The average mass of a carbon atom is 12.011 this is due to isotopes of carbon. No carbon atom has the mass 12.011 amu because this is not the exact mass, but this is the average mass of isotopes of carbon. Since, different isotopes have different masses, the atomic mass of the carbon in periodic table is written by taking average of atomic masses of its isotopes in accordance to their abundance.

c. heat could easily travel through the molecules in the air and escape/enter the flask. removing the air slows down the heat transfer.  

the answer is:  

line graphs show patterns in data with variables that change over time; whereas, circle graphs show data as parts out of a whole (such as out of 100%).