Hi, this sounds like a chemistry question:
If you wanted to separate sand from iron fillings for example, using tweezers would be a great tool to do this, depending on the size of the iron fillings.
I think the answer for this question is c
Answer:
New force, 
Explanation:
Given that, two point charges attract each other with an electric force of magnitude F. It is given by :

If one charge is reduced to one-third its original value and the distance between the charges is doubled such that,
, 



So, the electric force between them is reduced to (1/12). Hence, the correct option is (d).