When a positively charged particle enters a uniform magnetic field with uniform velocity, its trajectory can be : (1) a straight line (2) a circle (3) a helix

• A

  (1) only
• B

  (1) or (2)
• C

  (1) or (3)
• Correct answer
  D

  any one of (1), (2) and (3)

Hence, the correct answer is option: 'D'.