Answer:
A. They must be the same shape.
D. They can be different sizes.
Explanation:
Similar shapes share all of their angles. Therefore, congruent shapes (shapes that are the same size) are similar, and dilated shapes (shapes that have been scaled by a constant proportion) are similar as well.
In this context, the "same shape" means a "dilated form of the same shape", so a "different shape" is actually a "different type of shape" (i.e., a circle is different from a square)