1] our house was once a stop on the underground railroad. [2] the underground railroad were a network of hiding places. [3] the cellar beneath our house has a secret door that was installed to trick slave catchers. [4] living in a piece of american history is pretty interesting. which sentence has a subject-verb agreement error?

Based on the sentences given, it is sentence 2 that has an error on subject-verb agreement. Notice that the subject is "Underground Railroad" and this is singular. Therefore, the verb that it should take is singular too. The correct verb to be used should be "was" and not "were". So the correct sentence is this: The Underground Railroad was a network of hiding places.

B for edgenuity when u r taking the quiz

That is an example of a demonstrative adjective

Further explanation

Demonstrative adjectives are words that modify nouns and identify a specific noun or nouns. The most common demonstrative adjectives are this, that, these and those:

The primary singular forms of demonstrative adjectives are:

This is used for a person or thing that is nearby or current . Example: This day could not get any better! That is used for a person or thing that is further away . Example: That house across the street is so adorable.  

Whereas the primary plural forms of demonstrative adjectives are:

These is used for more than one thing that's nearby . Example: These shoes fit me very well. Those is used for more than one thing that's farther away .  Example: Those boots are too expensive.

There are some examples of demonstrative adjectives and their use in the sentence:

That dog is really sick and need care. This uniform I’m wearing is very neat and clean. That plane has to be landed one hour later. These boots are too expensiveThese clothes smell very dirty.

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Grade:  9

Subject:  

Chapter:  demonstrative adjective

Keywords:  demonstrative adjective