If points \( T \) and \( T' \) have the same x-coordinate after reflection, that means the reflection is occurring across a horizontal line.
Let's analyze the options:
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The line of reflection is the x-axis.
- If \( T \) is reflected over the x-axis, then the y-coordinate changes sign while the x-coordinate remains the same. This would yield \( T' \) with the same x-coordinate but a different y-coordinate.
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The line of reflection is the y-axis.
- If \( T \) is reflected over the y-axis, the x-coordinate changes sign while the y-coordinate remains the same. In this case, \( T' \) would have a different x-coordinate, so this option is not valid.
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The line of reflection is vertical.
- If the line of reflection is vertical (which would generally be something like the y-axis), it would cause the points to have a different x-coordinate after reflection. Therefore, this option is not valid.
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The line of reflection is horizontal.
- A horizontal line means that the y-coordinate is unchanged, while the x-coordinate remains the same. Thus, \( T \) and \( T' \) would have the same x-coordinate if reflected over a horizontal line.
Based on this reasoning, the correct answer is:
The line of reflection is horizontal.
This is the only option that allows for points \( T \) and \( T' \) to have the same x-coordinate during the reflection process.