Classify each random variable as discrete or continuous.
a. The number of votes necessary to elect a new Pope.
b. The amount of sugar in a 16-ounce sweetened bottled drink purchased in a New York City cafe.
c. The total number of riders on all forms of public transportation in the United States during the year.
d. The number of residents in an assisted-living center who suffer from hardening of the arteries.
e. The amount of lead measured in the soil of a children's playground.
f. The time it takes an automobile to pass through the George Massey Tunnel in Vancouver, British Columbia.