[单选题]
A Styrofoam ball of mass 0.120 g i)c+ hj8da:lsw k w7pfd5fom99ke*2 smx wjckd d2n/v8b-n5 b /s placed in an electric field of 6000 N/C pointing downward. What charge must be placed on the ball for it to be suspendednfkk*27mv 5-mbdwn2f9oxsb/95jk c8dwe pd/?
