Which structure is used to transfer macromolecules between the cytoplasm and the nucleus?

The nucleus is a membrane-bound organelle that contains the cell's genetic material in the form of DNA. It is separated from the cytoplasm by a double membrane known as the nuclear envelope. The nuclear envelope contains small, cylindrical structures called nuclear pores that regulate the movement of molecules between the nucleus and the cytoplasm.

Macromolecules, such as proteins and RNA molecules, are too large to pass through the nuclear envelope by diffusion. Instead, they must be actively transported through the nuclear pores.

Nuclear pores on the nuclear envelope facilitate the movement of macromolecules between the cytoplasm and nucleus. The nuclear pore complex, which is made up of nuclear pores, as well as the nucleus's inner and outer membranes, is responsible for this transport. Therefore, the correct answer is nuclear pores.