Questions: A nuclear pore is best described as an opening in the that permits the passage of molecules into and out of the nucleus. nucleolus endoplasmic reticulum plasma membrane nuclear envelope

The answer is the last one (or D): nuclear envelope.

Explanation for each option:

• Nucleolus: The nucleolus is a dense region within the nucleus where ribosomal RNA (rRNA) is synthesized and ribosome assembly begins. It is not involved in the passage of molecules into and out of the nucleus.
• Endoplasmic reticulum: The endoplasmic reticulum (ER) is an organelle involved in protein and lipid synthesis. It is not directly involved in the transport of molecules into and out of the nucleus.
• Plasma membrane: The plasma membrane surrounds the cell and regulates the movement of substances into and out of the cell, but it is not specific to the nucleus.
• Nuclear envelope: The nuclear envelope is a double membrane structure that surrounds the nucleus. It contains nuclear pores, which are openings that permit the passage of molecules such as RNA and proteins into and out of the nucleus.

Summary: The nuclear pore is best described as an opening in the nuclear envelope that permits the passage of molecules into and out of the nucleus.