By adding a vibration at the natural frequency of the medium-A
Answer is c that is he particles move perpendicular to the direction of the wave.
Answer:
Deltoid Force, 
Additional Information:
Some numerical information are missing from the question. However, I will derive the formula to calculate the force of the deltoid muscle. All you need to do is insert the necessary information and calculate.
Explanation:
The deltoid muscle is the one keeping the hand arm in position. We have two torques that apply to the rotating of the arm.
1. The torque about the point in the shoulder for the deltoid muscle,
2. The torque of the arm,
Assuming the arm is just being stretched and there is no rotation going on,
= 0
= 0
⇒ 

Where,
is radius of the deltoid
is the force of the deltiod
is the angle of the deltiod
is the radius of the arm
is the force of the arm ,
which is the mass of the arm and acceleration due to gravity
is the angle of the arm
The force of the deltoid muscle is,

but
,
∴ 
Answer:The choke coil works because it can act as an inductor. When the current pass through will change as AC currents creates a magnetic field in the coil that works against that current. This is known as inductance and blocks most of the AC current from passing through.
Explanation: