Which of the following correctly describes the nature of electric field lines? 

(A) They can cross if two fields intersect: Electric field lines never cross. If they did, at the point of intersection, a test charge placed there would experience force in two different directions simultaneously, which is not possible. The electric field at any point has a unique direction. Therefore, this statement is incorrect.   (B) They start from negative and end on positive charges: Electric field lines originate from positive charges and terminate on negative charges. The direction of the electric field is defined as the direction of the force on a positive test charge. Therefore, this statement is incorrect.   (C) They represent the direction of force on a negative test charge: Electric field lines represent the direction of the force on a positive test charge. The force on a negative test charge would be in the opposite direction to the electric field line at that point. Therefore, this statement is incorrect.   (D) They never form closed loops: Electric field lines due to electrostatic fields (fields produced by stationary charges) never form closed loops. They originate from positive charges and end on negative charges (or extend to infinity). Closed loops of electric field lines are associated with changing magnetic fields (as described by Faraday's law of induction), which is not the case for electrostatic fields. Therefore, this statement is correct.   Therefore, the correct answer is option (D).