The role of active cytotoxic t cells is to attack the role of active cytotoxic t cells is to attack extracellular viruses and bacteria body cells that have been infected circulating proteins complement proteins circulating antibodies

The role of active cytotoxic t cells is to attack  cancer cellsm body cells that have been infected and damaged in other ways. extracellular viruses and bacteria body cells that have been infected circulating proteins complement proteins circulating antibodies.

- a cytotoxic t cell is also know as killer cell. they can recognize a specific antigen - which is a foreign material or body. 

Humans can affect weathering and erosion in several ways.  humans cause  increases in acid rain and pollution, which increase the amount of  weathering  agents in the air and water, and then on land.for an easy answer: 1) acid rain2) pollution