Which of the following statements is true about the U.S. Senate?
a. Its members have six-year terms, with one-third of the total members up for re-election every two years.
b. Its members have six-year terms, with the majority of its members facing re-election every four years.
c. Its members have two-year terms, with one-third of the total members up for re-election every two years.
d. Its members have two-year terms, with the majority of its members facing re-election every four years.