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: There was an immense scowl on her face.

SOLUTION: Singular

PROBLEM: His thumbs were tracing patterns on my face, and it was hard to think or form coherent responses.

SOLUTION: Plural

PROBLEM: The healers buy their supplies from herbalists instead of foraging for them.

SOLUTION:
Plural