Case A:
→E=0
⇒→FE=0
If initial velocity →v is at an angle to →B, there will be a component along →B and a component ⊥→B
The ⊥ component is responsible for circular motion in the plane ⊥ to →B.
The parallel component to →B is responsible for motion along →B.
If →v∥→B, the motion will be along →B only.
Case B:
If →v∥to→E, there will be acceleration if charge is positive, deceleration if the charge is negative.
If →v∦to→E, the trajectory will be a parabola.
Case C:
→E≠0
→B≠0
→E∥→B
Path will be helical since component ∥→B and vecE will move the particle along this direction.
Component ⊥→B will make the particle move in a circle.
Hence, the combined motion will be helical.
Case D:
→E≠0
→B≠0
→v⊥→E
→v⊥→B
→Fmag∥→E or →Fmag∥(−→E)
Hence, path will be a parabola in general.
If →Fmag∥(−→E) and both magnitudes are equal, the path will be a straight line.
Hence,
A→1,3
B→1,2
C→4
D→1,2