Which one of the following is an example of cross-section data?

Which one of the following is an example of cross-section data?

Select one:

a. total insect population among 12 U.S. national parks in 2003b. consumption (in pounds) of pork products in the U.S. from 1983 to 2003c. daily checking account balance last yeard. total value of U.S. Savings Bonds each year from 1994 to 2004