Stones used for ornamental work must be A. Soft B. Hard C. Light D. Heavy

The correct answer is: B. Hard

Stones used for ornamental work must be hard because they need to be able to withstand the elements and wear and tear. Soft stones would not be able to withstand these conditions and would quickly deteriorate.

Option A is incorrect because soft stones are not durable enough for ornamental work. They would easily scratch or break.

Option C is incorrect because light stones are not as stable as heavy stones. They would be more likely to topple over or be blown away by the wind.

Option D is incorrect because heavy stones are more stable than light stones. They are also less likely to be blown away by the wind.