Water trap is used for

Answer: Option D

Water trap is used for WBPH.
White Backed Plant Hopper (WBPH) is the bioassay on F3 pyramided transgenic rice lines along with parents and control plants.
The water trap provides a water seal between the appliance and the external drains or outside atmosphere.
The water trap will prevent smells, insects and bacteria from coming back up the waste pipework into your building. The trap will only work and prevent smells when it has water inside which provides the water seal.