(i) Inside a solenoid, the magnetic field lines are parallel and straight, indicating that the magnetic field is uniform inside the solenoid.
(ii) Around a straight current-carrying conductor, the magnetic field lines form concentric circles around the wire, as given by the right-hand thumb rule. Therefore, the correct shapes are: - Solenoid: straight field lines - Straight conductor: circular field lines So, the correct answer is (a) straight and circular.