Tell whether each of the following involves a categorical variable, a discrete quantitative variable, or a continuous quantitative variable.
a. Depth of fish fossils found below the sea floor
b. Whether a country's government pays for at least half of higher education costs
c. How many evenings a student went out in the week preceding a survey
d. The proportion of higher education costs paid by the government in each of many countries around the world
e. Vertical drop of various ski slopes
f. Body mass of dinosaur specimens
g. Number of 2004 Olympic medals won by various countries