During which process does one bacterium inject its DNA into another
bacterium through a thin tube called a pilus?

DNA is transferred from one bacterium to another. After the donor cell pulls itself close to the recipient using a structure called a pilus, DNA is transferred between cells. In most cases, this DNA is in the form of a plasmid. An F+ donor cell contains its chromosomal DNA and an F plasmid

Pancreassalivary glandsliverlachrymal glandssweat glandoil glandsgoblet cells