16. Which ONE of these lamps is used for street lighting a. mercury halide b. high pressure sodium c. low pressure mercury vapour d. high pressure mercury vapour. 17. The base diameter of an area protected by a lighting mast is 50cm. The height of the arrestor is a. 100m b. 75m c. 50m d. 25m.

b. High pressure sodium---# Explanation:## The base diameter of the area protected by a lightning mast is related to its height through trigonometry using tangent function.### ### Given that cm corresponds to half the diameter or radius of the circle (base), we can calculate for the height as follows: ## Therefore, based on this calculation:- If \(θ ≈ arctan(4) ≈ 75°\), then - Option A would result in a very tall structure which seems impractical, - Options C and D do not provide enough clearance from ground level considering typical applications, - Hence, option B ( ) appears most reasonable given practical considerations.# Answer: b.