Which Priority Instruction or Precaution Does the Nurse Teach a Client

Which priority instruction or precaution does the nurse teach a client who is scheduled for a positron emission tomography scan of the brain?

A) "Avoid caffeine-containing substances for 12 hours before the test."
B) "Drink at least 3 liters of fluid during the 24 hours after the test."
C) "Do not take your cardiac medication on the morning of the test."
D) "Remove your dentures and any metal before the test begins."