Answer: C. Rectangles 1 and 3
Explanation:
1. By definition, two rectangles are similar if they have equal shape bot do not have equal sizes.
2. You can know it the rectangle 1 and 3 are similar by the following proportions:

Where
is the lenght of the rectangle 1,
is the lenght of the rectangle 2,
is the width of the rectangle 1 and
is the width of the rectangle 2.
3. Subtitute values:


4. Then, the rectangle 1 and 3 are similar.