Some  cells are able to directly kill tumor cells and virall…

Some  cells are able to directly kill tumor cells and virally infected cells by specifically recognizing cell surface antigens and then producing and releasing cytotoxic granules that lead to apoptosis.  Which of the following cells directly kill tumor cells and virally infected cells in this manner?

During the season a sport psychologist has the football play…

During the season a sport psychologist has the football players practice imagery after first watching a videotape in which they are performing the same skill as the one they intend to image. The coaches can’t believe how quickly the players improved their performance and consistency. What is the best explanation for the preceding?