Answer:
I think its C and D
Explanation:Force is like a energy that moves stuff. :)
To solve this problem we will apply the concepts related to Coulomb's law for which the Electrostatic Force is defined as,

Here,
k = Coulomb's constant
= Charge at each object
r = Distance between them
As the distance is doubled so,





Therefore the factor is 1/4
Explanation:
(a) Since, it is given that the blocks are identical so distribution of charge will be uniform on both the blocks.
Hence, final charge on block A will be calculated as follows.
Charge on block A =
= 4.35 nC
Therefore, final charge on the block A is 4.35 nC.
(b) As it is given that the positive charge is coming on block A
. This means that movement of electrons will be from A to B.
Thus, we can conclude that while the blocks were in contact with each other then electrons will flow from A to B.