[单选题]
An electron is held up against oh rtp2jz xv5-.s.m9xh,.ib rthe force of gravity by the attraction u) ok(h3: d+g rf n2merl5fb9mof a fixed proton some diek 2bg3 m hm(frnl5+9)ur:odf stance above it. How far above the electron is the proton?
A. $1.5 \; m$
B. $2.3 \; m$
C. $3.7 \; m$
D. $5.1 \; m$
