It is likely C, the Senate and the house of representatives...
Demographers are scientists who study human populations. They tend to map and understand the dynamics of population, which includes birth, death, and migration. All of these affects population and must be studied by demographers. They may study the population change within a country or the interrelationship of countries' populations, which is mostly necessary in studying migration. However, they could also take specialization. For example, they could study only parts of the population like workers' social pattern. Demographers mainly use statistics in mapping their data.
