Based on the side lengths alone, could the triangles be similar?

Yes they could be simiualr

Step-by-step explanation:

one is just bigger than the other

Explanation:

The defining characteristic of a rectangle is that there are 4 right angles (90 degree angles) as shown by the square markers in each corner. This is all that you need to say this figure is a rectangle. Further information you could use to add onto your proof is that the opposite sides are congruent. The congruent segments share the same number of tickmarks.

It is not a rhombus as not all four sides are the same length. The same reasoning applies to a square as well. Any square is also a rhombus. So we can cross choice B and choice C off the list.