Which of the following has sunken stomata?

Acacia have sunken stomata which arranged in deep pits (sunken) to minimise water loss through transpiration. They are present in plants like Acacia, Pine, Opuntia, etc., that are usually in areas of water scarcity i.e., arid areas or deserts where to prevent water loss due to transpiration. Hydrilla (stomata may be present on upper surface of the leaf), Vallisneria (stomata are absent) and Zostera (stomata are absent) are aquatic plants.