A. Sinus bradycardia

a. often occurs naturally.

b. is considered abnormal in athletes.

c. is often seen in Wolff–Parkinson–White syndrome.

d. is caused by increased sympathetic stimulation.

B.  Characteristics of sinus bradycardia include

a. PR intervals that change.

b. inverted P waves in lead II.

c. a regular rhythm.

d. wide, bizarre QRS complexes.

C. Sinus tachycardia

a. has mostly the same characteristics as normal sinus rhythm except that it

has a rate of greater than 120 beats per minute.

b. is produced by stimulation of the parasympathetic branch of the

autonomic nervous system.

c. may be caused by ingestion of caffeine or alcohol, smoking, or fever.

d. continues even after the stimulus causing it is removed.