Which of the following is not a valid conversion factor? 1/100 centimeter 1ml/1cm^3 1kilometer/1000 meters 1meter/10 milimeters

1meter/10 milimeters which should be 1000 mm

1m=1000mm

International System of Units (SI Units) are organized body of measurements for physical quantity. They are set to be the norm or global norm scaling for every physical quantity which includes kilogram, meter, second, ampere, kelvin, candela and mole. These measurements then can increase or decrease by the power of ten, multiplied or divided. As said and explained, the SI is helpful in describing objects because 
1.       They give us the idea of how much matter is contained in that single substance or the current state the matter is in or how hot or cold. We measure and can quantify the quality of the specific matter. 
2.       SI Units are a global set of measurement hence, we can communicate with ease from western to eastern countries with these measurements without having problems in terms of portraying or displaying a set of physical quantities. 

Answer : option a) 84explanation :

considering the question as per the attachment

here we can see that the radon nuclide has 222 as the atomic mass number and 86 as the atomic number.

when it undergoes nuclear fission it gives polonium which has atomic mass number as 218 and atomic number will be 84 along with a helium nucleus which has 4 atomic mass number and 2 as its atomic number.

222 = 218 + 4 (atomic mass number)

86 = ? + 2; therefore ? = 86-2 = 84.

the atomic mass number of polonium will be 84.