I believe the answer is c
Electrostatic forces between charges depend on the product of
the sizes of the charges, and the distance between them.
We should also mention the item about whether the charges are
both the same sign or opposite signs. That determines whether
the forces will pull them together or push them apart, which is a
pretty significant item.
Answer:
d= 7.32 mm
Explanation:
Given that
E= 110 GPa
σ = 240 MPa
P= 6640 N
L= 370 mm
ΔL = 0.53
Area A= πr²
We know that elongation due to load given as



A= 42.14 mm²
πr² = 42.14 mm²
r=3.66 mm
diameter ,d= 2r
d= 7.32 mm