Right choice is (b) 45 cm
Easiest explanation: A flush toilet may be colloquially called a lavatory, water closet (abbreviated W.C.), loo, comfort room (abbreviated C.R.), and many other names.
A flush toilet is a toilet that disposes of human excreta (urine and feces) by using water to flush it through a drainpipe to another location for disposal, thus maintaining a separation between humans and their excreta. Flush toilets can be designed for sitting (in which case they are also called “Western” toilets) or for squatting, in the case of squat toilets. The opposite of a flush toilet is a dry, which uses no water for flushing.