6. Assuming the exit speed of cannonballs is always the same when fired from the cannon. If the angle of the cannon is φ when aiming at a target 800 m away, what is the condition on angleθ when aiming at 300 m away?(A) sin(2θ) =sin(2φ) (B) cos(θ) =cos(φ) (C) tan(θ) =tan(φ) (D) tan(θ) =tan(φ)