Identify the given type of hydroponic technique and select the correct option.

Answer: DSolution: The given figure represents the nutrient film technique of hydroponics. In this technique, a very shallow stream of water containing all the dissolved nutrients requried for plant growth is recirculated past the bare roots of plants in a water tight channel. the depth of the recirculating stream is very shallow (thin film) ,which ensures that the thick root and mat, which develops at the bottom of the channel, has an upper surface in sufficient supply of air/oxygen. The main advantage o f this system is that the plant roots are exposed to adequate quantities of water, $O_2$ and nutrients.