I believe the correct answer is the second option. The type of decay that characterizes the change of nuclides to their respective daughter products would be exponential decay. This type of decay is characterized by the decrease of quantity of a material according to the equation y=ab^x.
The two ways to measure the sand in a sand castle are by counting the number of pails of sand used to build the castle and by determining the mass of the sand used in building the castle. The first method makes use of the volume of the pail to determine the amount of sand while the second method is a more quantitative way.<span />
</u></em>