Final answer:
The side length of Emma's photo is 2 inches.
Step-by-step explanation:
To find the side length of Emma's photo, we can use the given scale from the canvas to the photo. If the scale is 5 in. to 1 in., then the photo is 1/5 the size of the canvas. Since the side length of the canvas is 10 in., the side length of the photo would be 10 in. divided by 5, which is 2 in. Therefore, the correct answer is option D) 2 in.