The correct option is
B Nephrocytes
The excretory organ of cockroach is the malpighian tubules. The nephrocyte in a cockroach is the lateral wall of their heart. This wall helps excretion and helps store waste. It is found at the junction of the midgut and hindgut and is about 150 in number. They are fine, yellow-coloured and branched threads present in bundles. They lie freely in the hemolymph. these cells are binucleated structures.
So the correct answer is 'Nephrocytes'.