31. The major second messengers are

A. cAMP
B. cGMP
C. DAG
D. All of these

32. The signaling molecules called steroid hormones

A. are made in one location of the body but have their effects some distance away
B. are hydrophilic and so cannot penetrate the plasma membrane
C. bind to cell surface receptors to trigger chemical cascades
D. never enter the blood of humans