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.

Washoe's progress with ASL was rapid ; by 1971, she had a vocabulary of 160 signs, which she used in conversation.
Singular

" Hey, " the rogue called, walking up to me.
Singular

Flames crackled in the night.

Plural