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.

Your skills are impeccable, but this program involves strict discipline.
Plural

The challenge in his voice startled her.
Singular

The nuns closed the outer door, locked it with the two beams and lowered the portcullis behind it.

Plural