Question

sponges generate a current through their bodies using flagella on their choanocytes flagella on their amebocytes flagella on their ostia flagella on their osculum

Explanation:

Sponges generate a water current through their bodies using the flagella of their choanocytes. Choanocytes are specialized cells in sponges with flagella that beat to create the current for filter - feeding. Amebocytes have other functions like nutrient transport, ostia are pores for water entry, and osculum is for water exit, not for generating the current.

Answer:

Flagella on their choanocytes