Answer:A
Explanation: Teacher gave me the answer
These unsegmented worms have a full digestive system even when parasitic.
As fas as i remember 20% of whole cell is RBC
so the answer is 2×10^13 !!
<span>The answer is B) cell wall. The cell wall is a structure important cell protection and shape. It is necessary for the survival of unicellular organisms, such as Archaea and bacteria. Plants, some fungi, and algae also have cell walls with major function in structural support and protection against environmental conditions and infection. However, animal cells do not have cell walls.</span>
