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: Their footsteps rang out on the concrete floor.

SOLUTION: Plural

PROBLEM: Their apartments were ten minutes apart and they each regularly dropped by the other's place.

SOLUTION: Plural

PROBLEM: ' No worries, father.

SOLUTION:
Plural