B. secrete granzymes and perforin.
Perforins are the proteins that perforate the plasma membrane of the target cell and lead to bursting of cells due to holes formed in its membrane. Granzymes are the proteolytic enzymes. They serve to stimulate the target cells to kill themselves by the process of apoptosis.
Binding of natural killer cells to their target cells stimulate the release of granules that are filled with perforins or granzymes to kill the target cells.
Likewise, cytotoxic T cells bind to the infected body cells and release the granules filled with perforins or granzymes to kill those infected cells.
i'm thinking (a) to keep sand in place; ////////////
explanation: a sand fence or sandbreak, like a snow fence, is used to force windblown, drifting sand to accumulate in a desired place. sand fences are employed to control erosion, sand dune stabilization, keep sand off roadways, and to recruit new material in desert areas.
a. secrete inter...