An aircraft moving with a speed of 1000 km/h is at a height of 6000 m, just overhead of an anti-aircraft gun. If the muzzle velocity of the gun is 540 m/s, the firing angle \[\theta \] for the bullet to hit the aircraft should be

• A. \[73{}^\circ \]
• B. \[30{}^\circ \]
• C. \[60{}^\circ \]
• D. \[45{}^\circ \]