Hume steel pipes are A. Steel pipes B. Steel shell coated from inside with cement mortar C. Steel shell coated from outside with cement mortar D. Both B and C

The correct answer is D. Both B and C.

Hume steel pipes are steel pipes that are coated with cement mortar on both the inside and outside. This coating provides corrosion protection and makes the pipes more durable. Hume steel pipes are commonly used in water and sewerage applications.

Option A is incorrect because it does not specify that the steel pipes are coated with cement mortar. Option B is incorrect because it does not specify that the steel pipes are coated with cement mortar on both the inside and outside. Option C is incorrect because it does not specify that the steel pipes are made of steel.