It could be B or D, but I am fairly certain it is D.
Reminder: The illustration mentioned in the inquiry is included here as a file.
Response:
The intensity of the magnetic field is 
Clarification:
The magnetic field can be calculated using the following equation:
...............(1)
Where I refers to the current flowing through the wires
To find the distance R from point 1 to m, apply the Pythagorean theorem


Inserting R into equation (1)


Response:
0.60 m/s
Details:
The average speed between times t = a and t = b can be expressed as:
v_avg = (x(b) − x(a)) / (b − a)
Given the function x(t) = 0.36t² − 1.20t, and considering the interval from 1.0 to 4.0:
v_avg = (x(4.0) − x(1.0)) / (4.0 − 1.0)
v_avg = [(0.36(4.0)² − 1.20(4.0)) − (0.36(1.0)² − 1.20(1.0))] / 3.0
v_avg = [(5.76 − 4.8) − (0.36 − 1.20)] / 3.0
v_avg = [0.96 − (-0.84)] / 3.0
v_avg = 0.60
The average speed calculated is 0.60 m/s.
If my calculations are accurate, the angle is 67.5 degrees.
The derived frequency equals 2.63 Hz. Explanation: For an object weighing 8.0 kg with a spring stretching 3.6 cm, calculations involving the spring constant and oscillation frequency lead to this specific oscillation rate.