Final answer:
The small structures within the cytoplasm that include the nucleus are organelles, fulfilling a variety of specialized functions that are essential for the cell's functioning.
Step-by-step explanation:
Cytoplasm contains many small structures; these structures, including the nucleus, are called organelles. The correct answer to the question is option C) Organelles. The cytoplasm, a jelly-like material present outside the nucleus, houses organelles and is the site of protein synthesis and various metabolic events. Organelles such as mitochondria, ribosomes, and elements of the cytoskeleton perform specialized functions that are essential for the cell's operation and maintenance.
For instance, mitochondria are known as the powerhouse of the cell due to their role in generating ATP (adenosine triphosphate), the cell's energy currency. Meanwhile, ribosomes are engaged in protein synthesis, an essential cellular process. The organelles and various structures within the cytoplasm enable eukaryotic cells to carry out more complex functions compared to prokaryotic cells, which do not compartmentalize their internal structures in the same way.