What are the filaments called that some bacteria stick to surfaces and exchange plasmids through conjugation?

The correct answer is pili or pilus.

Explanation:

The filaments or hair-like appendages found on the surface of the bacteria and help some bacteria stick to surfaces and exchange plasmids through conjugation. Pili attach itself to other bacteria surface and facilitate the transfer of genetic material. These pili are also known as sex-pili as it draws matting cells in close contact.

the solute can move "downhill," from regions of higher to lower concentration, relying on the specificity of the protein carrier to pass through the membrane. this process is called passive transport or facilitated diffusion, and does not require energy.