I think the answer is proton
Answer:
1. The proton is deflected toward the east by the magnetic force, but its kinetic energy does not change
Explanation:
This is consequently because the magnetic field unlike the electric field, deflects the electron but does not change its speed or kinetic energy.
To solve this problem we must keep in mind the concepts related to angular kinematic equations. For which the angular velocity is defined as

Where
Final angular velocity
Initial angular velocity
Angular acceleration
t= time
In this case we do not have a final angular velocity, then

Re-arrange for 



Therefore the mangitude of the angular aceleration is 5449.1rad/s²