Teacher: In this task you are given a sentence. You must judge whether the object of the main clause is singular(like: apple) or plural(like: apartments). Label the instances as "Singular" or "Plural" based on your judgment.
Teacher: Now, understand the problem? If you are still confused, see the following example:
They both let out relieved breaths at the doctor's words.
Solution: Plural
Reason: "relieved breaths" is the object of the sentence which is plural.

Now, solve this instance: He's reworking the spell detector so this type of thing won't happen again.
Student:
Singular