The aqueduct or superpassage type of works are generally used when A. high flood drainage discharge is small B. high flood drainage discharge is large and short lived C. high flood drainage discharge is large and continues for a long time D. none of the above

The correct answer is: C. high flood drainage discharge is large and continues for a long time.

Aqueducts or superpassages are structures that carry water across a valley or other low-lying area. They are typically used when the flood drainage discharge is large and continues for a long time. This is because aqueducts or superpassages can provide a continuous path for water to flow, even when the water level is high.

Option A is incorrect because aqueducts or superpassages are not typically used when the flood drainage discharge is small. This is because aqueducts or superpassages are expensive to build, and they are not necessary when the flood drainage discharge is small.

Option B is incorrect because aqueducts or superpassages can be used when the flood drainage discharge is large and short lived. However, they are not typically used in these cases because other, less expensive structures, such as floodplains, can be used to manage the floodwaters.

Option D is incorrect because aqueducts or superpassages are a type of structure that is used to manage floodwaters.