Which of the following is a complex solution outside the cell nucleus contained by a cell membrane?

The cytoplasm is indeed considered a complex solution outside the cell nucleus contained by a cell membrane. It encompasses all the materials within the cell membrane that are not part of the nucleus. This includes various organelles, such as the endoplasmic reticulum and Golgi apparatus, as well as cytosol, which is the fluid component where many metabolic processes occur.

The cytoplasm plays a critical role in cellular function, providing a medium for the biochemical activities necessary for the cell's survival, growth, and replication. It contains enzymes, ions, and small molecules that facilitate metabolic reactions and serve as a site for many cellular processes.

In contrast, the endoplasmic reticulum and Golgi apparatus are specific organelles within the cytoplasm that serve distinct functions, such as protein synthesis and processing. The nucleus, on the other hand, is the control center of the cell housing the genetic material but is not part of the cytoplasm. Thus, identifying the cytoplasm correctly emphasizes its importance as a complex solution necessary for cellular function.