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: The shadowy grotto had disappeared.

SOLUTION: Singular

PROBLEM: When my tender skin has toughened enough to withstand the pressure of sheets, more visitors arrive.

SOLUTION: Plural

PROBLEM: Besides, the parking spaces here are tiny.

SOLUTION:
Plural