21. Evidence in support of the importance of endosymbiosis in the evolution of eukaryotic cells is:
a, Organelles that have their own unique unique DNA and ribosomes
Organelles that have a double membrane
6. Organelles are in the same size range as free living prokaryotes
d. All of the above

d. All of the above

Explanation:

The theory of endosymbiosis is important as it explains the evolution of  eukaryotic cells from prokaryotic cells.

This theory also explains the origin of chloroplast and mitochondria. Several evidences in support of the importance of endosymbiosis in the evolution of  eukaryotic cells are as following:

Chloroplast and mitochondria are the examples of such organelles.

Hence, the correct answer is "d".

organ system-an organ system is a group of organs that work together to perform one or more functions. each does a particular job in the body, and is made up of certain tissues.