A traditional method of water conservation used in Karnataka:

Drip irrigation
Sprinkler irrigation
Tanks (Kere)
Canal irrigation

The correct answer is C. Tanks (Kere).

Tanks (Kere) are traditional water conservation structures used in Karnataka. They are man-made reservoirs that collect rainwater and store it for use during the dry season. Tanks are an important source of water for irrigation, drinking water, and domestic use. They also play an important role in flood control and recharging groundwater aquifers.

Drip irrigation is a method of irrigation that delivers water directly to the roots of plants, using a network of small pipes and emitters. This method of irrigation is very efficient, as it minimizes water loss due to evaporation and runoff. Drip irrigation is also very effective in reducing soil erosion and nutrient leaching.

Sprinkler irrigation is a method of irrigation that uses sprinklers to spray water onto crops. This method of irrigation is less efficient than drip irrigation, as it results in more water loss due to evaporation and runoff. However, sprinkler irrigation is often used in areas where water is plentiful and where the topography is not suitable for drip irrigation.

Canal irrigation is a method of irrigation that uses canals to transport water from a source, such as a river or a reservoir, to fields where it is used to irrigate crops. This method of irrigation is often used in large-scale agricultural operations. Canal irrigation can be a very efficient method of irrigation, but it can also be very expensive to construct and maintain.

In conclusion, the correct answer to the question “A traditional method of water conservation used in Karnataka” is C. Tanks (Kere).