Which of the following statements is false?

Which of the following statements is false?
  a. Tobacco smoking is the most serious risk factor
  for cardiovascular disease.
  b. Until age 50, males have a greater risk of a heart
  attack than females.
  c. Hypertension is called the silent killer.
  d. In atherosclerosis, the diameter of the lumen of a
  blood vessel decreases.
  e. If a blood clot becomes dislodged and travels in
  the bloodstream, it is called a thrombus.

Question 2

The most dangerous type of arrhythmia is
  a. tachycardia.
  b. ventricular fibrillation.
  c. brachycardia.
  d. atrial fibrillation.
  e. an electrocardiogram.