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: Bit dangerous, to be seen visiting so often.

SOLUTION: Singular

PROBLEM: Ahead of the ship, the relatively calm seas were washing against slate grey rocks that rose seven or eight feet up out of the waters.

SOLUTION: Plural

PROBLEM: The author of these emails is powerful and a force to be reckoned with.

SOLUTION:
Singular