The correct answer is B. select.
To select means to choose from a number of possibilities. In this case, the committee is choosing the team that will represent them in the tournament.
The other options are not as accurate. To appoint means to give someone a position of authority. To elect means to choose someone by voting. To nominate means to suggest someone for a position.
In this case, the committee is not giving someone a position of authority, they are not choosing someone by voting, and they are not suggesting someone for a position. They are simply choosing the team that will represent them in the tournament.