Question

Why is syntax important in a piece of writing?

Answer 1

Syntax are important in a piece of writing because it is essential for written communication. 
Without syntax, the sentences are harder to understand. 

Example:   Incorrect: While watching a movie, people who text on their phone are very annoying
                  Correct: People who text on their phone while watching a movie are very annoying. 

It just makes the sentence easier to understand. 

Hope that helps! 

Answer 2

A  is the correct answer.