In a eukaryotic cell, the non-organelle part of the cell among the options provided is:
C) Cytoplasm
The cytoplasm is the material within a cell, excluding the nucleus, and it contains various components including organelles like mitochondria and ribosomes. Ribosomes are not membrane-bound organelles, but they are often categorized with organelles due to their role in protein synthesis. The nucleus and mitochondria are both membrane-bound organelles.