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: A trickle of something simmered in my gut and the buzz of anxiety spread.

SOLUTION: Singular

PROBLEM: The shadowy grotto had disappeared.

SOLUTION: Singular

PROBLEM: Reyes opened his eyes, awakened by a shaft of golden sunlight filtering through the cottage's single window.

SOLUTION:
Plural