[单选题]
An electron is held up ag/h.zx7:/:f*v g ovl yj .iwrzqyug/ l-as 7*h:eqln9b finst the force of gravity by the attraction of a fixed proton some distance above q9:sfh* n7el bit. How far above the electron is the proton?
A. $1.5 \; m$
B. $2.3 \; m$
C. $3.7 \; m$
D. $5.1 \; m$
