[ Answer ]
Mounted on the dash of a car, a GPS replaces paper maps.
[ Answer ]
Option A does not include a comma before the word car, an after the letter a. Without this comma, we have a run-on sentence. A run-on sentence is multiple sentences with no punctuation to separate them. In order to avoid a run on sentence, we need to add punctation to our sentences.
Run-on sentence eg:
Jack ran a marathon he absolutely loved it.
Corrected run-on sentence:
Jack ran a marathon. He absolutely loved it.
Adding punctuation between sentences makes the sentence clear and easy to understand, and it avoids creating a run-on sentence.
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