Question

Which pair of triangles can be proven congruent by SAS?

2 identical triangles are shown. The triangle is reflected across a line to form the second triangle.
2 identical triangles are shown. The triangle is rotated 90 degrees to form the second triangle.
2 identical triangles are shown. The triangle is reflected across a line and then rotated to form the second triangle.
2 identical triangles are shown. The triangle is rotated up and to the left 90 degrees to form the second triangle.

Answer 1

All of them.

Reflections and rotations are rigid motions, so they preserve all side lengths and angle measures. For any corresponding pair of sides and the angle between them you pick, those two sides and that included angle are equal in the image triangle, so SAS applies.