A transformation maps (1,0)→(0,1)(1, 0) \rightarrow (0, 1)(1,0)→(0,1) and (0,1)→(−1,0)(0, 1) \rightarrow (-1, 0)(0,1)→(−1,0). What is this transformation?
90∘90^\circ90∘ counter-clockwise rotation
90∘90^\circ90∘ clockwise rotation
Reflection across y=xy=xy=x
Reflection across y=−xy=-xy=−x