The correct answer is $\boxed{\text{B}}$.
The range of a projectile is the maximum horizontal distance it travels. The angle of projection is the angle between the initial velocity vector and the horizontal.
For a given initial velocity, the range is maximized when the angle of projection is 45°. This is because the horizontal component of the initial velocity is equal to the vertical component of the initial velocity at this angle. This means that the projectile spends the same amount of time in the air, and therefore travels the same horizontal distance, regardless of its initial height.
At angles of projection less than 45°, the horizontal component of the initial velocity is greater than the vertical component. This means that the projectile spends more time in the air, and therefore travels a greater horizontal distance. However, it also means that the projectile reaches a lower maximum height.
At angles of projection greater than 45°, the vertical component of the initial velocity is greater than the horizontal component. This means that the projectile reaches a higher maximum height, but it also means that it spends less time in the air, and therefore travels a shorter horizontal distance.
Therefore, the angle of projection that maximizes the range is 45°.