How do leaders in both chambers of Congress exert their power?

The floor leaders and whips of each party are elected by a majority vote of all the senators of their party assembled in a conference or, as it sometimes is called, a caucus. The practice has been to choose the leader for a two-year term at the beginning of each Congress.

Explanation:

d. direct

2018 means 2018 ce or common era

there have been other eras too including bce, which included way more years.