A plurality is when a candidate or option receives more votes than any other, but not necessarily a majority (which would require more than half). Based on this definition, the following options from your list are examples of a plurality:
- 1,550 of the Democrat Party's 4,765 delegates prefer a candidate. (This indicates that this candidate has more support than others, but it's not specified if it's a majority.)
- 205 of 538 members of the Electoral College vote for a president. (This could represent a plurality depending on how many votes other candidates received, but it doesn't need to be a majority.)
The other options indicate either a majority (more than half) or unanimous support:
- 370 of 435 members of Congress support a bill. (This is a majority.)
- 51 of 100 senators support a judicial nominee. (This is a majority.)
- 9 of 9 Supreme Court justices support a decision. (This is unanimous support.)
So the correct selections for examples of a plurality are:
- 1,550 of the Democrat Party's 4,765 delegates prefer a candidate.
- 205 of 538 members of the Electoral College vote for a president.