$($A$)$ The magnetic force acting on this charged particle at the location shown in the figure above is

$,$ and it points $.$ If the proton is replaced by an electron. the direction of magnetic force acting on the electron will be

$($B$)$ The particle $($proton$)$ will trace a $$ circle of radius $$ mm in the magnetic field due to the magnetic force.

$($C$)$ The work done by the magnetic force on this proton is $$ because