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: If I worked fast enough, adrenaline put up a wall between me and my throbbing headache.

SOLUTION: Singular

PROBLEM: A few minutes later I returned, hair combed and teeth brushed, too.

SOLUTION: Plural

PROBLEM: My mattress caved in from the pressure of his knee, and I squeezed my legs together.

SOLUTION:
Plural