Water comes out through _____, once it enters into the spongocoel through minute pores called ostia in sponges.

The correct option is A Osculum
Sponges which are generally marine have a unique feature, which is the canal system. Water enters through minute pores called ostia in the body wall into a central cavity, spongocoel, from where it goes out through the osculum. This pathway of water transport is helpful in food gathering, respiratory exchange and removal of waste.