TASK DEFINITION: In this task you are given a sentence. You must judge whether subject of the main clause is singular or plural. Label the instances as "Singular" or "Plural" based on your judgment.
PROBLEM: His thrusts slowed down to an unbearably slow pace.

SOLUTION: Plural

PROBLEM: Strangely, their full garb that was perfectly natural in 1831 also seemed natural for standing in the middle of Schuylkill River Park.

SOLUTION: Singular

PROBLEM: A rider on a fast horse might even make it to the gates first and alert the guard. "

SOLUTION:
Singular