Ascaris has ______________ cells in the excretory system

The correct option is Renette cells.

Here is a step-by-step explanation of the excretory system in Ascaris:

1. Introduction to Ascaris:
Ascaris lumbricoides is a giant roundworm belonging to the phylum Nematoda (Aschelminthes). Unlike other complex animals, nematodes have a simplified body plan with specialized structures suited for their parasitic lifestyle.

2. The Excretory Organ:
The excretory system of Ascaris is H-shaped and consists of a single, large, giant cell called the Renette cell (or Renette gland cell). In Ascaris, this gland cell is developed into two longitudinal excretory canals running along the lateral sides of the body, which are joined near the anterior end by a transverse network of canals.

3. Elimination of Waste:
These canals collect nitrogenous waste products (mainly in the form of ammonia and urea) from the pseudocoelomic fluid and eliminate them through a single excretory pore located on the ventral side near the anterior end of the worm.

4. Comparing Other Options:
- Green glands: These are the excretory organs found in crustaceans like prawns.
- Flame cells: These are specialized excretory and osmoregulatory cells found in flatworms (phylum Platyhelminthes).
- Nephrons: These are the basic structural and functional units of the kidneys found in vertebrates.

Therefore, the excretory system of Ascaris is uniquely characterized by the presence of Renette cells.