Answer:
A, C
Explanation:
You want all the shapes that are enlargements of shape X, which is 1 unit high and 3 units wide.
Enlargement
An enlargement of shape X multiplies each of its dimensions by the same factor. When it is enlarged by a factor of 2, the dimensions become ...
high : wide = 1 : 3 = 2 : 6 . . . . . . matches shape C
When it is enlarged by a factor of 3, the dimensions become ...
high : wide = 1 : 3 = 3 : 9 . . . . . . . matches shape A
The 2-high shape B is too short, being 4 1/2 wide instead of 6. Shape F is too long, being 7 wide instead of 6.
The 3-high shapes D and E are too short, being 8 and 5 wide instead of 9.
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Additional comment
An enlargement preserves the aspect ratio of the shape, the height to width ratio. Here, that is 1:3. Any shape with a different aspect ratio is not an enlargement of X.