C

Step 1: Analyze the assertion - In javelin throw, the athlete throws the projectile at an angle less than 45 degrees. This is true because optimal angle for maximum range in projectile motion is indeed less than 45 degrees due to the need to account for the javelin's aerodynamic properties.

Step 2: Analyze the reason - The maximum height of the projectile does depend on the angle of projection. A higher angle can produce a higher maximum height, even though the range might be maximized around 30-35 degrees for javelin throws.

Therefore, the assertion is true but the reason is false. Consequently, the correct choice is C.