:2. Diagram ? on page ? shows a histogram for the blood
pressures of subjects in a certain survey, along with the normal
curve which approximates it.  The percentage who had blood
pressures between 120mm and 140mm is exactly equal to
 
 	
 a. 40%  <p>

b. the area under the histogram between 120 and 140  <p>

c. the area under the normal curve between 120 and 140  <p>

d. 100% <p>

e. 0% <p>