The correct option is (C): 1287
Explation: To find out how many bars of soap the company sold, we can calculate 20% of the total stock of soap, which is 6,435 bars.
Calculate 20% of 6,435:
\[\text{Number of bars sold} = \frac{20}{100} \times 6435 = 0.2 \times 6435 = 1287\]
So, the company sold 1,287 bars of soap.
The answer is Option C: 1287.