A dust particle in the Millikan-style setup builds up a static charge of exactly three fundamental units. Given that these drops accumulate charge as excess electrons, what is the sign and rough size of the drop's charge, using the elementary charge e = 1.602 x 10^-19 C?

1. The oil drops in this experiment pick up excess electrons, so their charge is negative. 2. Three fundamental units of charge means three electron charges: 3 x 1.602 x 10^-19 C = 4.806 x 10^-19 C in magnitude. 3. Rounding to three significant figures gives 4.81 x 10^-19 C, and the sign is negative. 4. Option B repeats a single unit of charge rather than three units, and option C drops the negative sign; option A also drops the sign, which is the classic sign trap when counting elementary charges. _Source: OpenStax Physics (CC BY 4.0), Ch 18 "Static Electricity", section Electric Charge_