Concept:For a projectile, the maximum range and maximum height are related through the angle of projection.Explanation:Maximum range, R=gu2sin2θMaximum height, H=2gu2sin2θGiven HR=4Substitute the expressions:2gu2sin2θgu2sin2θ=4sin2θ2sin2θ=4Since sin2θ=2sinθcosθ, we get:sin2θ4sinθcosθ=4sinθcosθ=1cotθ=1θ=45∘Answer:The angle of projection is 45∘, which is option C.