Which of the following statements about PCIe connectors on a motherboard that supports up-plugging are correct?

Up-plugging allows you to fit a smaller PCIe card into a larger slot even if it does not completely fill it. For example, an x8 card can be inserted into an x16 slot. The x8 card will not fill the entire slot, but it will operate at x8 speeds. It's crucial to note that not all motherboards offer this ability, so if you want to put a smaller card in a larger PCIe slot, make sure the motherboard supports up-plugging, else the card will only work at 1x speed.