Answer:
1st one
Explanation:
Rotation: Turn
Clockwise: The direction a clock turns, right.
2, 3, and 4 are not correct because 2 is a translation, or a slide. 3 includes more than one rigid transformations, and 4 is a reflection.
When you turn bottom left triangle one more time to the right, it will fit into the top left triangle. There is no need to reflect or translate the shape.