A Muonic Hydrogen Atom Is a Proton Orbited by a Muon

Multiple Choice

A muonic hydrogen atom is a proton orbited by a muon (a particle with the same charge as an electron and 207 times its mass) in which the mass of the muon is significant relative to the mass of the proton.What would be the radius of the smallest muon orbit in a muonic hydrogen atom?

A) 1.03 × 10^-8 m
B) 1.10 × 10^-8 m
C) 2.56 × 10^-13 m
D) 2.84 × 10^-13 m
E) 5.29 × 10^-11 m