Look at the figure below:

triangle srp has measure of angle srp equal to 90 degrees. q is a point on the hypotenuse sp such that the segment qr is perpendicular to ps. t is a point outside the triangle on the left of s so that triangle qts has the measure of angle qts equal to 90 degrees.

which triangle is similar to triangle pqr?

triangle rqs
triangle qts
triangle stq
triangle spr