Look at the picture below. the boy is swinging back and forth on the swing. at which point is the potential energy of a swing the least? point a (at the top) point b (halfway back) point c (at the bottom) point d (halfway up)

Since this motion is without any friction force or any other resistive   force so energy is being conserved here

So we can say sum of kinetic energy and potential energy will remain conserved

So here we can say

so here if KE is maximum then PE will become minimum and vice versa

so during to and fro motion kinetic energy is maximum at the bottom most position and hence due to conservation of energy when kinetic energy is maximum then potential energy must be minimum.

so correct answer is

Point C (at the bottom)

a.metals can become magnetic if they have many spinning electrons that create magnetic fields.d.only some metals are attracted by magnets; these metals are called ferromagnetic.

d.wrapping an insulated wire around a metal with ferromagnetic properties and applying an electric current.

vapour or gas assuming atmospheriv pressure