____ tennis player created one of the major Grand Slams upsets by knocking out Roger Federer from US Open ?

a) Grigor Dimitrov
b) Andy Murray
c) Dominic Thiem
d) Marin Cilic

Five-time Champion Roger Federer was knocked out of the US Open after losing to Grigor Dimitrov in the quarterfinals on September 3, 2019.  Dimitrov, ranked 78th, made a dramatic fightback to defeat the third seed Federer 3-6, 6-4, 3-6, 6-4, 6-2 at Arthur Ashe Stadium. He will face fifth seed Russian Medvedev in the semis.