Pick Up the Incorrect Statement Regarding a Master Trap from the Following

Multiple Choice

Pick up the incorrect statement regarding a master trap from the following:

A) it is provided in between the lower end of the house drain and the street sewer
B) it is provided a cleaning eye at the top of the trap
C) the mica flap valve which opens inwards only, is fitted at the top of the inlet pipe
D) the water seal is less than that of ordinary traps