T cells and B cells can be activated only by
A) pathogens.
B) interleukins, interferons, and colony-stimulating factors.
C) cells infected with viruses, bacteria, or cancer cells.
D) exposure to a specific antigen at a specific site in a plasma membrane.
E) disease-causing agents.
Question 2
The pyramidal system provides
A) voluntary control over skeletal muscles.
B) voluntary control over smooth muscles.
C) involuntary control over skeletal muscles.
D) involuntary control over smooth muscles.
E) involuntary control over cardiac muscle.