Final answer:
The nucleus is not a nonmembrane organelle, as it is surrounded by a nuclear membrane.
Step-by-step explanation:
A nonmembrane organelle is a cellular structure that is not enclosed within a membrane. Examples of nonmembrane organelles include ribosomes, centrosomes, and golgi apparatus. However, the nucleus is not a nonmembrane organelle, as it is surrounded by a nuclear membrane. Therefore, the correct answer is d) Nucleus.