Questions 23 to 25 are based on the conversation you have just heard.

A. In the air.
B. On the airfield.
C. Under water.
D. At plane manufacturing factory.

A. It breaks into the cell and reproduces itself.
B. It uses the CD4 receptor to bind with the RNA of the cell.
C. It integrates into the DNA of infected cells.
D. It destroys the cell’s RNA and multiplies inside it.