Answer: D - pili
bacteria communicate and exchange genetic information through extensions of their cell walls called 'pili'.
Step-by-step explanation:
Pili are found in bacteria and archaea surfaces as thin, rigid, hair-like fiber made of protein. They aid attachment of various bacteria cells to surfaces and other cells.
Pili are antigenic. They act as binding site for other cells like viruses and bacteria cells.
When pilus of a bacterium binds another bacterium cell (recipient cell), the single strand DNA is transferred to the recipient cell. Among the types of pili, the conjugative pili are known for communication and exchange of genetic informations between bacteria cells. The conjugative pili are also known as 'sex pili'. Exchange of DNA occurs after attachment of the donor to the recipient. The donors (bacteria cells with conjugative pili) attach to the recipients (bacteria without conjugative pili), connecting cytoplasm of both cells and promoting exchange of genetic materials including transfer of pili to the recipient cell.