Which Technique Is Correct When the Nurse Is Assessing the Radial

Which technique is correct when the nurse is assessing the radial pulse of a patient?
The pulse is counted for:

A) 1 minute, if the rhythm is irregular.
B) 15 seconds and then multiplied by 4, if the rhythm is regular.
C) 2 full minutes to detect any variation in amplitude.
D) 10 seconds and then multiplied by 6, if the patient has no history of cardiac abnormalities.