[单选题]
A Styrofoam ball of mass 0.120 g is placed ia v6u*k x*lw8d bvj1l:rqd t/i(;*tfz*p0dbrr93xg tw4j: kxn an electric field of 6000 N/C pointing downward. What charge must be placed on the ball for it to be suspe (rgdpr0/ qb;dttx *9:4zk*ifrw j t3xnded?
