It should be D, cells are parts, tissue is part and organ is part of a system.
i don't know but try putting this diagram into a question on google. you should be able to get some type of answer if not the right answer. good luck and * hint* you can make a really good question out of the sentence on top of the DIAGRAM. I hope this was helpful. please let me know in the comments: )
Explanation:
No of molecules=0.500×6.023×10²³=3.011×10²³ molecules
