Hint:- If a charge \\\\(q\\\\) is moving with velocity \\\\(v\\\\) in a Magnetic Field \\\\(B\\\\), such that angle between velocity of charge and Magnetic Field is \\\\(\ heta\\\\). Then Force acting on charge is given by,\\\\(F = qvBsin\ heta\\\\)Step 1: Note the given values and calculate force on an electron in magnetic field.\\\\(\\bullet\\\\) It is given that an electron is projected with uniform velocity along the axis of current carrying long solenoid. Let charge on electron is \\\\(e\\\\) and uniform velocity of electron is \\\\(v\\\\). Also let at any point on axis of solenoid Magnetic Field is \\\\(B\\\\).\\\\(\\bullet\\\\) We know that Magnetic Field on axis of solenoid is always parallel to the axis. And since electron is moving along axis of solenoid, we have \\\\(\ heta = 0°\\\\) or \\\\(\ heta = 180°\\\\). In both the cases value of \\\\(\\sin\ heta\\\\) is zero. \\\\(\\bullet\\\\) Thus net force acting on electron, that is \\\\(F = qvBsin\ heta = 0\\\\)Step 2: Explanation for options:-\\\\(\\bullet\\\\) Since net force on electron is zero, by Newton's Second Law its acceleration will be zero. Option A is incorrect.\\\\(\\bullet\\\\) Also since net force on electron is zero, its direction of motion will not change. So Option B is incorrect.\\\\(\\bullet\\\\)As theta is zero not 45 so option C is incorrect.\\\\(\\bullet\\\\) As net force is zero so net acceleration is zero. So the electron will continue to move along the axis with same velocity.Thus, only Option D is correct.