The Physician Has Ordered 6 Mg Morphine Sulphate Every Three

The physician has ordered 6 mg morphine sulphate every three to four hours prn for a patient's postoperative pain.The unit dose in the medication dispenser has 15 mg in 1 mL.How much solution should the nurse give?

A) 1.5 mL
B) 1.3 mL
C) 0.4 mL
D) 1.25 mL