Answer:
Charge,

Step-by-step explanation:
Mass of the particle, m = 1.7 g = 0.0017 kg
Electric field, E = 700 N/C
We need to find the charge particle to remain balanced against gravity when placed in a downward-directed electric field. So,
q E = m g


q = 0.0000238 C

So, the magnitude of charged particle is
. As the direction of electric field is in downward direction, so the charge is negative. Hence, this is the required solution.